Cranial Nerve Palsies

Overview

Definitions

• Palsy: paralysis of an area of the body, rendering it incapable of voluntary movement
• Cranial nerve (CN) palsy: dysfunction of a CN (in individuals with motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology function, may cause weakness or paralysis of the territory it innervates)

Overview of CNs

The table below summarizes the functions of the 12 CNs.

Cranial Nerve I (Olfactory) Palsy

Epidemiology

• Disorders of olfaction Olfaction The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy affect 10%‒12% of individuals > 40 years of age.
• Prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency increases with age to up to approximately 40% at age 80.
• Affects more men than women
• Affects more non-Whites than Whites

Etiology

• Sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis
• Allergic rhinitis Allergic rhinitis An inflammation of the nasal mucosa triggered by allergens. Rhinitis
• Viral infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease:
  • COVID-19 COVID-19 Coronavirus disease 2019 (COVID-19) is an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that mainly affects the respiratory system but can also cause damage to other body systems (cardiovascular, gastrointestinal, renal, and central nervous systems).
  • Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza
  • Common cold Common cold A catarrhal disorder of the upper respiratory tract, which may be viral or a mixed infection. It generally involves a runny nose, nasal congestion, and sneezing. Rhinovirus
• Nasal passage obstruction
• Migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache (olfactory aura Aura Reversible neurological phenomena that often precede or coincide with headache onset. Migraine Headache)
• Inhalant toxicity Toxicity Dosage Calculation:
  • Cigarette smoke
  • Herbicides
  • Pesticides
  • Solvents
• Medications (list is not exhaustive):
  • Antibiotics
  • Anticonvulsants
  • Antidepressants
• Nutritional deficiencies:
  • Vitamin A Vitamin A Retinol and derivatives of retinol that play an essential role in metabolic functioning of the retina, the growth of and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Dietary vitamin A is derived from a variety of carotenoids found in plants. It is enriched in the liver, egg yolks, and the fat component of dairy products. Fat-soluble Vitamins and their Deficiencies
  • Vitamins B6, B12
  • Zinc Zinc A metallic element of atomic number 30 and atomic weight 65. 38. It is a necessary trace element in the diet, forming an essential part of many enzymes, and playing an important role in protein synthesis and in cell division. Zinc deficiency is associated with anemia, short stature, hypogonadism, impaired wound healing, and geophagia. It is known by the symbol zn. Trace Elements, copper Copper A heavy metal trace element with the atomic symbol cu, atomic number 29, and atomic weight 63. 55. Trace Elements
• Tumor Tumor Inflammation/ mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast effect
• Limbic system Limbic system The limbic system is a neuronal network that mediates emotion and motivation, while also playing a role in learning and memory. The extended neural network is vital to numerous basic psychological functions and plays an invaluable role in processing and responding to environmental stimuli. Limbic System: Anatomy stroke/trauma
• Amyloid deposition disease
• Head trauma Head trauma Head trauma occurs when external forces are directed to the skull and brain structures, resulting in damage to the skull, brain, and intracranial structures. Head injuries can be classified as open (penetrating) or closed (blunt), and primary (from the initial trauma) or secondary (indirect brain injury), and range from mild to severe and life-threatening. Head Trauma/trauma to the cribriform plate
• Neurodegenerative disorders:
  • Huntington disease Huntington disease Huntington disease (HD) is a progressive neurodegenerative disorder with an autosomal dominant mode of inheritance and poor prognosis. It is caused by cytosine-adenine-guanine (CAG) trinucleotide repeats in the huntingtin gene (HTT). The most common clinical presentation in adulthood is a movement disorder known as chorea: abrupt, involuntary movements of the face, trunk, and limbs. Huntington Disease
  • Parkinson disease Parkinson disease Parkinson’s disease (PD) is a chronic, progressive neurodegenerative disorder. Although the cause is unknown, several genetic and environmental risk factors are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Parkinson’s Disease
  • Alzheimer disease Alzheimer disease As the most common cause of dementia, Alzheimer disease affects not only many individuals but also their families. Alzheimer disease is a progressive neurodegenerative disease that causes brain atrophy and presents with a decline in memory, cognition, and social skills. Alzheimer Disease
• Age-related deterioration in olfactory acuity

Pathophysiology

• CN I contains “special” afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology fibers that carry the sense of smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy.
• Specialized olfactory sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology cells are located in the olfactory mucosa Olfactory mucosa That portion of the nasal mucosa containing the sensory nerve endings for smell, located at the dome of each nasal cavity. The yellow-brownish olfactory epithelium consists of olfactory receptor neurons; brush cells; stem cells; and the associated olfactory glands. Olfaction: Anatomy underlying the cribriform plate:
  • Chemosensory neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology that have receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors for airborne odor molecules
  • Nasal mucosa Nasal mucosa The mucous lining of the nasal cavity, including lining of the nostril (vestibule) and the olfactory mucosa. Nasal mucosa consists of ciliated cells, goblet cells, brush cells, small granule cells, basal cells (stem cells) and glands containing both mucous and serous cells. Nose Anatomy (External & Internal) also produces mucus to “trap” odor molecules, facilitating receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors binding.
• Olfactory cells synapse Synapse The junction between 2 neurons is called a synapse. The synapse allows a neuron to pass an electrical or chemical signal to another neuron or target effector cell. Synapses and Neurotransmission with secondary neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology in the olfactory bulbs, which then transmit fibers to the limbic system Limbic system The limbic system is a neuronal network that mediates emotion and motivation, while also playing a role in learning and memory. The extended neural network is vital to numerous basic psychological functions and plays an invaluable role in processing and responding to environmental stimuli. Limbic System: Anatomy ( olfactory cortex Olfactory cortex Basal forebrain and medial part of temporal lobe areas that receive synaptic inputs from the olfactory bulb. Olfaction: Anatomy and amygdala Amygdala Almond-shaped group of basal nuclei anterior to the inferior horn of the lateral ventricle of the temporal lobe. The amygdala is part of the limbic system. Limbic System: Anatomy):
  • Olfactory cortex Olfactory cortex Basal forebrain and medial part of temporal lobe areas that receive synaptic inputs from the olfactory bulb. Olfaction: Anatomy functions to process and interpret olfactory stimuli.
  • Amygdala Amygdala Almond-shaped group of basal nuclei anterior to the inferior horn of the lateral ventricle of the temporal lobe. The amygdala is part of the limbic system. Limbic System: Anatomy may produce emotional responses and/or memories in response to olfactory stimuli.
• Any disruption to the neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology/olfactory pathway could result in dysfunction in sensing or processing smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy.

Clinical presentation

• Hyposmia: reduced ability to smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy
• Hyperosmia: abnormally enhanced sense of smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy
• Dysosmia: abnormal perception Perception The process by which the nature and meaning of sensory stimuli are recognized and interpreted. Psychiatric Assessment of smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy to familiar stimuli
• Anosmia:
  • Complete inability to smell Smell The sense of smell, or olfaction, begins in a small area on the roof of the nasal cavity, which is covered in specialized mucosa. From there, the olfactory nerve transmits the sensory perception of smell via the olfactory pathway. This pathway is composed of the olfactory cells and bulb, the tractus and striae olfactoriae, and the primary olfactory cortex and amygdala. Olfaction: Anatomy
  • May be unilateral or bilateral
• Olfactory hallucinations Hallucinations Subjectively experienced sensations in the absence of an appropriate stimulus, but which are regarded by the individual as real. They may be of organic origin or associated with mental disorders. Schizophrenia:
  • Perception Perception The process by which the nature and meaning of sensory stimuli are recognized and interpreted. Psychiatric Assessment of smells for which no stimulus is present
  • Often by irritation to the uncus Uncus Cerebral Cortex: Anatomy
  • Termed cacosmia if olfactory hallucination Hallucination Subjectively experienced sensations in the absence of an appropriate stimulus, but which are regarded by the individual as real. They may be of organic origin or associated with mental disorders. Schizophrenia is unpleasant
• May be related to disorders of taste sensation

Diagnosis

• Based on history and physical examination (rule out sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis, allergic rhinitis Allergic rhinitis An inflammation of the nasal mucosa triggered by allergens. Rhinitis, viral upper respiratory infection Upper respiratory infection Rhinitis (URI), medications)
• Test the affected individual with familiar scents while their eyes are closed.
• Labs:
  • CBC
  • Basic metabolic panel Basic Metabolic Panel Primary vs Secondary Headaches
  • Vitamin/mineral panel
  • Erythrocyte sedimentation rate Erythrocyte Sedimentation Rate Soft Tissue Abscess ( ESR ESR Soft Tissue Abscess)
• Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant (rule out mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast effect):
  • CT for evaluation of bony structures and/or paranasal sinuses Paranasal Sinuses The 4 pair of paranasal sinuses include the maxillary, ethmoid, sphenoid, and frontal sinuses. The sinuses are a group of air-filled cavities located within the facial and cranial skeleton; all are connected to the main nasal cavity and nasopharynx. Paranasal Sinuses: Anatomy
  • MRI for evaluation of soft tissue Soft Tissue Soft Tissue Abscess structures

Management

• Treat the underlying causes:
  • Allergic rhinitis Allergic rhinitis An inflammation of the nasal mucosa triggered by allergens. Rhinitis
  • Sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis
  • Remove obstructions.
• Smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases cessation
• Discontinue offending medications.
• Refer to ENT/for surgical evaluation for masses/tumors.
• Steroid burst and taper may have some utility for inflammatory conditions.

Differential diagnoses

• Intranasal substance use disorder
• Psychosis
• Migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache 
• Seizure disorder

Cranial Nerve II (Optic) Palsy

Epidemiology

• Optic neuritis is the most common cause of optic nerve Optic nerve The 2nd cranial nerve which conveys visual information from the retina to the brain. The nerve carries the axons of the retinal ganglion cells which sort at the optic chiasm and continue via the optic tracts to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the superior colliculi and the suprachiasmatic nuclei. Though known as the second cranial nerve, it is considered part of the central nervous system. The 12 Cranial Nerves: Overview and Functions dysfunction.
• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: approximately 6 per 100,000
• Affects more women than men, 3:1
• Affects more Caucasians than African Americans

Etiology

• Optic neuritis:
  • Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
  • Multiple sclerosis Sclerosis A pathological process consisting of hardening or fibrosis of an anatomical structure, often a vessel or a nerve. Wilms Tumor
• Stroke
• Tumor Tumor Inflammation
• Glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma (increased pressure on the optic nerve Optic nerve The 2nd cranial nerve which conveys visual information from the retina to the brain. The nerve carries the axons of the retinal ganglion cells which sort at the optic chiasm and continue via the optic tracts to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the superior colliculi and the suprachiasmatic nuclei. Though known as the second cranial nerve, it is considered part of the central nervous system. The 12 Cranial Nerves: Overview and Functions)
• Ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage
• Trauma
• Migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache
• Seizure

Pathophysiology

• CN II contains “special” afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology fibers that carry the sense of sight.
• Specialized photoreceptor sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology cells (retinal ganglion cells Ganglion Cells The Visual Pathway and Related Disorders) are located on the retina Retina The ten-layered nervous tissue membrane of the eye. It is continuous with the optic nerve and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the choroid and the inner surface with the vitreous body. The outermost layer is pigmented, whereas the inner nine layers are transparent. Eye: Anatomy on the posterior aspect of the eye:
  • The axons Axons Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body. Nervous System: Histology of these cells converge to form the optic nerves, optic chiasm Optic Chiasm The x-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes. The Visual Pathway and Related Disorders, and optic tracts.
  • The majority of retinal ganglion cells Ganglion Cells The Visual Pathway and Related Disorders are involved in image generation, whereas a minority are involved in reflex arcs and maintenance of the circadian rhythm.
• Retinal ganglion cells Ganglion Cells The Visual Pathway and Related Disorders synapse Synapse The junction between 2 neurons is called a synapse. The synapse allows a neuron to pass an electrical or chemical signal to another neuron or target effector cell. Synapses and Neurotransmission with secondary neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology at several target structures:
  • Suprachiasmatic nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles (in the hypothalamus Hypothalamus The hypothalamus is a collection of various nuclei within the diencephalon in the center of the brain. The hypothalamus plays a vital role in endocrine regulation as the primary regulator of the pituitary gland, and it is the major point of integration between the central nervous and endocrine systems. Hypothalamus, involved in circadian rhythms)
  • Lateral geniculate nucleus Lateral Geniculate Nucleus The Visual Pathway and Related Disorders (in the thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy, projects superior and inferior fibers to the primary visual cortex Primary Visual Cortex The Visual Pathway and Related Disorders of the occipital lobe Occipital lobe Posterior portion of the cerebral hemispheres responsible for processing visual sensory information. It is located posterior to the parieto-occipital sulcus and extends to the preoccipital notch. Cerebral Cortex: Anatomy)
  • Pretectal nucleus Pretectal Nucleus Pupil: Physiology and Abnormalities ( pupillary light reflex Pupillary Light Reflex Constriction of the pupil in response to light stimulation of the retina. It refers also to any reflex involving the iris, with resultant alteration of the diameter of the pupil. Pupil: Physiology and Abnormalities)
  • Superior colliculus (influences eye movements in response to environmental stimuli)
  • Primary visual cortex Primary Visual Cortex The Visual Pathway and Related Disorders (functions to process and interpret visual stimuli)
• Optic nerve Optic nerve The 2nd cranial nerve which conveys visual information from the retina to the brain. The nerve carries the axons of the retinal ganglion cells which sort at the optic chiasm and continue via the optic tracts to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the superior colliculi and the suprachiasmatic nuclei. Though known as the second cranial nerve, it is considered part of the central nervous system. The 12 Cranial Nerves: Overview and Functions also carries the afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology stimulus for pupillary light reflex Pupillary Light Reflex Constriction of the pupil in response to light stimulation of the retina. It refers also to any reflex involving the iris, with resultant alteration of the diameter of the pupil. Pupil: Physiology and Abnormalities and accommodation Accommodation Refractive Errors reflex:
  • Pupillary light reflex Pupillary Light Reflex Constriction of the pupil in response to light stimulation of the retina. It refers also to any reflex involving the iris, with resultant alteration of the diameter of the pupil. Pupil: Physiology and Abnormalities: Optic nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology synapse Synapse The junction between 2 neurons is called a synapse. The synapse allows a neuron to pass an electrical or chemical signal to another neuron or target effector cell. Synapses and Neurotransmission at the Edinger-Westphal nucleus Edinger-Westphal Nucleus Nucleus in the oculomotor nuclear complex associated with oculomotor activities and stress adaptation. Pupil: Physiology and Abnormalities, where efferent Efferent Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology fibers of CN III are stimulated to constrict the pupil Pupil The pupil is the space within the eye that permits light to project onto the retina. Anatomically located in front of the lens, the pupil’s size is controlled by the surrounding iris. The pupil provides insight into the function of the central and autonomic nervous systems. Pupil: Physiology and Abnormalities.
  • Accommodation Accommodation Refractive Errors reflex:
    • Optic nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology synapse Synapse The junction between 2 neurons is called a synapse. The synapse allows a neuron to pass an electrical or chemical signal to another neuron or target effector cell. Synapses and Neurotransmission at the primary visual cortex Primary Visual Cortex The Visual Pathway and Related Disorders, where efferent Efferent Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology signals synapse Synapse The junction between 2 neurons is called a synapse. The synapse allows a neuron to pass an electrical or chemical signal to another neuron or target effector cell. Synapses and Neurotransmission at the Edinger-Westphal nucleus Edinger-Westphal Nucleus Nucleus in the oculomotor nuclear complex associated with oculomotor activities and stress adaptation. Pupil: Physiology and Abnormalities and oculomotor nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles.
    • Efferent Efferent Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology fibers of CN III are stimulated to constrict the pupil Pupil The pupil is the space within the eye that permits light to project onto the retina. Anatomically located in front of the lens, the pupil’s size is controlled by the surrounding iris. The pupil provides insight into the function of the central and autonomic nervous systems. Pupil: Physiology and Abnormalities and relax the ciliary muscles Ciliary Muscles Pupil: Physiology and Abnormalities, such that refraction Refraction Refractive Errors of the lens Lens A transparent, biconvex structure of the eye, enclosed in a capsule and situated behind the iris and in front of the vitreous humor (vitreous body). It is slightly overlapped at its margin by the ciliary processes. Adaptation by the ciliary body is crucial for ocular accommodation. Eye: Anatomy is manipulated.
• Best-described pathologic mechanisms of CN II dysfunction for optic neuritis:
  • Inflammatory demyelination Demyelination Multiple Sclerosis of the optic nerve Optic nerve The 2nd cranial nerve which conveys visual information from the retina to the brain. The nerve carries the axons of the retinal ganglion cells which sort at the optic chiasm and continue via the optic tracts to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the superior colliculi and the suprachiasmatic nuclei. Though known as the second cranial nerve, it is considered part of the central nervous system. The 12 Cranial Nerves: Overview and Functions manifests as:
    • Retinal vascular endothelial inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation
    • Perivascular cuffing
    • Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema of myelinated Myelinated Internuclear Ophthalmoplegia nerve sheaths
  • Thought to be an immune-mediated condition
  • Genetic susceptibility related to human leukocyte antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination (HLA) subtypes is likely.

Clinical presentation

• Visual field Visual Field The Visual Pathway and Related Disorders impairment/visual loss:
  • Optic nerve injury Nerve Injury Surgical Complications anterior to the optic chiasm Optic Chiasm The x-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes. The Visual Pathway and Related Disorders → ipsilateral monocular vision Vision Ophthalmic Exam loss
  • Optic chiasm Optic Chiasm The x-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes. The Visual Pathway and Related Disorders injury disrupts the medial (nasal) retinal fibers of both eyes Both Eyes Refractive Errors → loss of both lateral (temporal) visual fields (bitemporal hemianopia Hemianopia Transient Ischemic Attack (TIA))
  • Optic tract Optic Tract Nerve fiber originating from the optic chiasm that connects predominantly to the lateral geniculate bodies. It is the continuation of the visual pathway that conveys the visual information originally from the retina to the optic chiasm via the optic nerves. The Visual Pathway and Related Disorders injury results in contralateral homonymous hemianopia Hemianopia Transient Ischemic Attack (TIA).
• Loss of color vision Vision Ophthalmic Exam out of proportion to visual acuity Visual Acuity Clarity or sharpness of ocular vision or the ability of the eye to see fine details. Visual acuity depends on the functions of retina, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast. Ophthalmic Exam (seen in optic neuritis)
• Diplopia Diplopia A visual symptom in which a single object is perceived by the visual cortex as two objects rather than one. Disorders associated with this condition include refractive errors; strabismus; oculomotor nerve diseases; trochlear nerve diseases; abducens nerve diseases; and diseases of the brain stem and occipital lobe. Myasthenia Gravis
• Scotoma
• Blindness Blindness The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of eye diseases; optic nerve diseases; optic chiasm diseases; or brain diseases affecting the visual pathways or occipital lobe. Retinopathy of Prematurity
• Pupillary dysfunction:
  • Loss of constriction
  • Loss of accommodation Accommodation Refractive Errors
• Eye pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
• Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways with eye movement

Diagnosis

• Visual field Visual Field The Visual Pathway and Related Disorders testing
• Visual acuity Visual Acuity Clarity or sharpness of ocular vision or the ability of the eye to see fine details. Visual acuity depends on the functions of retina, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast. Ophthalmic Exam testing (Snellen chart)
• Color vision Vision Ophthalmic Exam testing ( Ishihara chart Ishihara Chart Ophthalmic Exam)
• Fundoscopy
• Intraocular pressure Intraocular Pressure The pressure of the fluids in the eye. Ophthalmic Exam monitoring
• Labs:
  • CBC
  • Serum glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance and HbA1c HbA1c Products of non-enzymatic reactions between glucose and hemoglobin a, occurring as a minor fraction of the hemoglobin components of human erythrocytes. Hemoglobin a1c is hemoglobin a with glucose covalently bound to the terminal valine of the beta chain. Glycated hemoglobin a is used as an index of the average blood sugar level over a lifetime of erythrocytes. Diabetes Mellitus
  • ESR ESR Soft Tissue Abscess
• Lumbar puncture Lumbar Puncture Febrile Infant with CSF studies:
  • Typical meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis/ encephalitis Encephalitis Encephalitis is inflammation of the brain parenchyma caused by an infection, usually viral. Encephalitis may present with mild symptoms such as headache, fever, fatigue, and muscle and joint pain or with severe symptoms such as seizures, altered consciousness, and paralysis. Encephalitis workup (includes studies for Lyme disease Lyme disease Lyme disease is a tick-borne infection caused by the gram-negative spirochete Borrelia burgdorferi. Lyme disease is transmitted by the black-legged Ixodes tick (known as a deer tick), which is only found in specific geographic regions. Patient presentation can vary depending on the stage of the disease and may include a characteristic erythema migrans rash. Lyme Disease, HSV HSV Herpes simplex virus (HSV) is a double-stranded DNA virus belonging to the family Herpesviridae. Herpes simplex virus commonly causes recurrent infections involving the skin and mucosal surfaces, including the mouth, lips, eyes, and genitals. Herpes Simplex Virus 1 and 2 infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease)
  • IgG IgG The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of igg, for example, igg1, igg2a, and igg2b. Hypersensitivity Pneumonitis levels, oligoclonal bands Oligoclonal bands Multiple protein bands serving as markers of specific antibodies and detected by electrophoresis of cerebrospinal fluid or serum. The bands are most often seen during inflammatory or immune processes and are found in most patients with multiple sclerosis. Multiple Sclerosis, myelin basic protein
• Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant (of brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and orbits):
  • CT for evaluation of bony structures
  • MRI (with contrast) for evaluation of soft tissue Soft Tissue Soft Tissue Abscess structures

Management

• Acute visual loss should prompt emergent ophthalmology referral.
• Steroid burst and taper may have some utility for inflammatory conditions.
• Disease-specific therapies for identifiable/treatable underlying causes
• Immune-modulation therapies for autoimmune disorders

Differential diagnoses

• Multiple sclerosis Sclerosis A pathological process consisting of hardening or fibrosis of an anatomical structure, often a vessel or a nerve. Wilms Tumor
• Autoimmune disease
• Deposition disease
• Meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis/ encephalitis Encephalitis Encephalitis is inflammation of the brain parenchyma caused by an infection, usually viral. Encephalitis may present with mild symptoms such as headache, fever, fatigue, and muscle and joint pain or with severe symptoms such as seizures, altered consciousness, and paralysis. Encephalitis
• Cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke
• Migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache
• Seizure disorder

Cranial Nerve III (Oculomotor) Palsy

Epidemiology

• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency of acquired CN III palsy: 4.0 per 100,000 people
• Affects men and women equally

Etiology

• Causes inherent to CN III:
  • Nerve ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage
  • Trauma
  • Intracranial neoplasm
  • Hemorrhage
  • Migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache
  • Congenital Congenital Chorioretinitis
  • Idiopathic Idiopathic Dermatomyositis
• Systemic causes:
  • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus
  • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension

Pathophysiology

• Oculomotor nerve Oculomotor nerve The 3D cranial nerve. The oculomotor nerve sends motor fibers to the levator muscles of the eyelid and to the superior rectus, inferior rectus, and inferior oblique muscles of the eye. It also sends parasympathetic efferents (via the ciliary ganglion) to the muscles controlling pupillary constriction and accommodation. The motor fibers originate in the oculomotor nuclei of the midbrain. The 12 Cranial Nerves: Overview and Functions has parasympathetic fibers in the outer layer (superficial) and the motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervating fibers centrally.
• Vascular supply differs between the outer (via blood vessels supplying the pia mater Pia mater The innermost layer of the three meninges covering the brain and spinal cord. It is the fine vascular membrane that lies under the arachnoid and the dura mater. Meninges: Anatomy) and inner (via vasa vasorum Vasa vasorum Nutrient blood vessels which supply the walls of large arteries or veins. Arteries: Histology) portions of the nerve:
  • Ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage is more likely to 1st cause damage to the inner layers ( motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology fibers).
  • Lesions that result in ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage cause more prominent motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology symptoms.
  • Compressive lesions of the nerves (e.g., aneurysms, mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast, herniations) are likely to present with the compromise of parasympathetic innervation (blown pupil Pupil The pupil is the space within the eye that permits light to project onto the retina. Anatomically located in front of the lens, the pupil’s size is controlled by the surrounding iris. The pupil provides insight into the function of the central and autonomic nervous systems. Pupil: Physiology and Abnormalities).

Clinical presentation

• Lesion of the motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology fibers (ipsilateral symptoms/findings):
  • Diplopia Diplopia A visual symptom in which a single object is perceived by the visual cortex as two objects rather than one. Disorders associated with this condition include refractive errors; strabismus; oculomotor nerve diseases; trochlear nerve diseases; abducens nerve diseases; and diseases of the brain stem and occipital lobe. Myasthenia Gravis (horizontal)
  • Ptosis
  • Weakness on adduction Adduction Examination of the Upper Limbs
  • Down-and-out (lateral and downward) gaze
• Lesion of the autonomic (parasympathetic) fibers (ipsilateral symptoms/findings):
  • Difficulty in accommodating between bright and dim lighting (ciliary muscle paralysis)
  • Fixed and mydriatic pupil Pupil The pupil is the space within the eye that permits light to project onto the retina. Anatomically located in front of the lens, the pupil’s size is controlled by the surrounding iris. The pupil provides insight into the function of the central and autonomic nervous systems. Pupil: Physiology and Abnormalities

Diagnosis

• Based on history and physical examination (pupillary and ocular motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology tests)
• Labs:
  • CBC
  • Serum glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance and HbA1c HbA1c Products of non-enzymatic reactions between glucose and hemoglobin a, occurring as a minor fraction of the hemoglobin components of human erythrocytes. Hemoglobin a1c is hemoglobin a with glucose covalently bound to the terminal valine of the beta chain. Glycated hemoglobin a is used as an index of the average blood sugar level over a lifetime of erythrocytes. Diabetes Mellitus
  • ESR ESR Soft Tissue Abscess
• Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant (1st-line modality for mydriatic pupils to identify compressive lesions):
  • CT
  • MRI

Management

Urgent:

• CN III palsy is an important sign indicating life-threatening aneurysms.
• All blown pupils must be examined using imaging to diagnose herniation Herniation Omphalocele.
• Urgent clipping of aneurysms

Nonurgent:

• Conservative:
  • Medical management
  • Monitor and manage diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus or demyelinating causes.
  • Follow-up every 3 months for signs of improvement.
• Surgical indications:
  • Cases that do not improve with conservative management
  • Goal: restoration of binocular vision Vision Ophthalmic Exam
  • Removal of intracranial masses

Differential diagnoses

• Congenital Congenital Chorioretinitis ptosis
• Anisocoria Anisocoria Unequal pupil size, which may represent a benign physiologic variant or a manifestation of disease. Pathologic anisocoria reflects an abnormality in the musculature of the iris (iris diseases) or in the parasympathetic or sympathetic pathways that innervate the pupil. Physiologic anisocoria refers to an asymmetry of pupil diameter, usually less than 2mm, that is not associated with disease. Pupil: Physiology and Abnormalities
• Ophthalmoplegic migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache
• Myasthenia gravis Myasthenia Gravis Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness and fatigability of skeletal muscles caused by dysfunction/destruction of acetylcholine receptors at the neuromuscular junction. MG presents with fatigue, ptosis, diplopia, dysphagia, respiratory difficulties, and progressive weakness in the limbs, leading to difficulty in movement. Myasthenia Gravis

Cranial Nerve IV (Trochlear) Palsy

Epidemiology

• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 5.73 per 100,000 individuals per year
• Men are more commonly affected in the 3rd decade of life.

Etiology

• Congenital Congenital Chorioretinitis
• Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
• Trauma
• Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
• After neurosurgery Neurosurgery Neurosurgery is a specialized field focused on the surgical management of pathologies of the brain, spine, spinal cord, and peripheral nerves. General neurosurgery includes cases of trauma and emergencies. There are a number of specialized neurosurgical practices, including oncologic neurosurgery, spinal neurosurgery, and pediatric neurosurgery. Neurosurgery
• Intracranial neoplasms Neoplasms New abnormal growth of tissue. Malignant neoplasms show a greater degree of anaplasia and have the properties of invasion and metastasis, compared to benign neoplasms. Benign Bone Tumors
• After herpes zoster ophthalmicus Herpes zoster ophthalmicus Virus infection of the gasserian ganglion and its nerve branches characterized by pain and vesicular eruptions with much swelling. Ocular involvement is usually heralded by a vesicle on the tip of the nose. This area is innervated by the nasociliary nerve. Herpes Zoster (Shingles)
• Cavernous sinus thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus

Clinical presentation

• Affected individuals usually complain of diplopia Diplopia A visual symptom in which a single object is perceived by the visual cortex as two objects rather than one. Disorders associated with this condition include refractive errors; strabismus; oculomotor nerve diseases; trochlear nerve diseases; abducens nerve diseases; and diseases of the brain stem and occipital lobe. Myasthenia Gravis while reading or going down the stairs.
• Vertical binocular diplopia Diplopia A visual symptom in which a single object is perceived by the visual cortex as two objects rather than one. Disorders associated with this condition include refractive errors; strabismus; oculomotor nerve diseases; trochlear nerve diseases; abducens nerve diseases; and diseases of the brain stem and occipital lobe. Myasthenia Gravis: exacerbated when the gaze is directed downward and inward
• Eye exam:
  • Extortion of the eye: When the subject is asked to abduct the eye while looking down, the eye shoots up on adduction Adduction Examination of the Upper Limbs.
  • Impaired intorsion, depression, and abduction Abduction Examination of the Upper Limbs of the eye (compromise of the superior oblique Superior oblique Orbit and Extraocular Muscles: Anatomy muscle) → induces overactivity of inferior oblique Inferior oblique Orbit and Extraocular Muscles: Anatomy muscle
  • Compensatory:
    • Strabismus Strabismus Strabismus is the misalignment of the eyes while fixating the gaze on an object. Strabismus can be idiopathic, but it may also be caused by cerebral palsy, uncorrected refractive errors, and extraocular muscle or cranial nerve dysfunction. Strabismus
    • Torticollis

Diagnosis

• Based on history and physical examination
• Additional studies are not required except to rule out differential diagnoses.

Management

• Conservative (expecting spontaneous recovery):
  • Prism glasses ( diplopia Diplopia A visual symptom in which a single object is perceived by the visual cortex as two objects rather than one. Disorders associated with this condition include refractive errors; strabismus; oculomotor nerve diseases; trochlear nerve diseases; abducens nerve diseases; and diseases of the brain stem and occipital lobe. Myasthenia Gravis)
  • Botulinum toxin Botulinum toxin Toxic proteins produced from the species Clostridium botulinum. The toxins are synthesized as a single peptide chain which is processed into a mature protein consisting of a heavy chain and light chain joined via a disulfide bond. The botulinum toxin light chain is a zinc-dependent protease which is released from the heavy chain upon endocytosis into presynaptic nerve endings. Once inside the cell the botulinum toxin light chain cleaves specific snare proteins which are essential for secretion of acetylcholine by synaptic vesicles. This inhibition of acetylcholine release results in muscular paralysis. Botulism injection into overactive inferior oblique Inferior oblique Orbit and Extraocular Muscles: Anatomy muscles
• Surgical:
  • Cases that do not improve with conservative management
  • Goal: restoration of binocular vision Vision Ophthalmic Exam
  • Inferior oblique Inferior oblique Orbit and Extraocular Muscles: Anatomy weakening + intervention of the vertical and horizontal recti

Differential diagnoses

• Myasthenia gravis Myasthenia Gravis Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness and fatigability of skeletal muscles caused by dysfunction/destruction of acetylcholine receptors at the neuromuscular junction. MG presents with fatigue, ptosis, diplopia, dysphagia, respiratory difficulties, and progressive weakness in the limbs, leading to difficulty in movement. Myasthenia Gravis
• Vestibulocochlear injury and skew deviation
• Orbital fractures Orbital fractures An orbital fracture is a break in the continuity of one or multiple bones of the eye socket, caused by direct or indirect trauma to the orbit. Patients frequently present with lacerations around the eye, orbital pain, edema, ecchymosis, diplopia on upward gaze, numbness around the eye, and signs of muscle entrapment. Orbital Fractures
• Congenital torticollis Congenital Torticollis Physical Examination of the Newborn
• Thyroid-associated ophthalmopathy ( TAO TAO A non-atherosclerotic, inflammatory thrombotic disease that commonly involves small and medium-sized arteries or veins in the extremities. It is characterized by occlusive thrombosis and fibrosis in the vascular wall leading to digital and limb ischemia and ulcerations. Thromboangiitis obliterans is highly associated with tobacco smoking. Thromboangiitis Obliterans (Buerger’s Disease))

Cranial Nerve V (Trigeminal) Palsy

Etiology

• Structural disorders:
  • Paget disease
  • Brainstem vascular loop
  • Syringobulbia
• Hereditary and degenerative disorders:
  • Neurofibromatosis
  • ALS ALS Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, is a sporadic or inherited neurodegenerative disease of upper motor neurons (UMNs) and lower motor neurons (LMNs). ALS is the most common progressive motor neuron disease in North America, primarily affecting men and individuals of Caucasian ethnicity. Amyotrophic Lateral Sclerosis
• Metabolic disorders:
  • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus
  • Thiamine Thiamine Also known as thiamine or thiamin, it is a vitamin C12H17N4OSCl of the vitamin B complex that is essential to normal metabolism and nerve function and is widespread in plants and animals Water-soluble Vitamins and their Deficiencies, folate Folate Folate and vitamin B12 are 2 of the most clinically important water-soluble vitamins. Deficiencies can present with megaloblastic anemia, GI symptoms, neuropsychiatric symptoms, and adverse pregnancy complications, including neural tube defects. Folate and Vitamin B12, vitamin B12 Vitamin B12 A cobalt-containing coordination compound produced by intestinal microorganisms and found also in soil and water. Higher plants do not concentrate vitamin B 12 from the soil and so are a poor source of the substance as compared with animal tissues. Intrinsic factor is important for the assimilation of vitamin B 12. Folate and Vitamin B12, pyridoxine, pantothenic acid, vitamin A Vitamin A Retinol and derivatives of retinol that play an essential role in metabolic functioning of the retina, the growth of and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Dietary vitamin A is derived from a variety of carotenoids found in plants. It is enriched in the liver, egg yolks, and the fat component of dairy products. Fat-soluble Vitamins and their Deficiencies deficiencies
• Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease:
  • Herpes zoster Herpes Zoster Varicella-zoster virus (VZV) is a linear, double-stranded DNA virus in the Herpesviridae family. Shingles (also known as herpes zoster) is more common in adults and occurs due to the reactivation of VZV. Varicella-Zoster Virus/Chickenpox
  • AIDS AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS (opportunistic infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease)
• Tumors:
  • CNS (e.g., glial tumors, meningioma Meningioma Meningiomas are slow-growing tumors that arise from the meninges of the brain and spinal cord. The vast majority are benign. These tumors commonly occur in individuals with a history of high doses of skull radiation, head trauma, and neurofibromatosis 2. Meningioma, schwannoma Schwannoma Schwannomas (also known as neurilemmomas) are benign nerve sheath tumors in the peripheral nervous system (PNS), arising from Schwann cells that encase the peripheral nerves. Schwannomas are the most common tumors in the PNS. Schwannoma)
  • Metastases (e.g., lung cancer Lung cancer Lung cancer is the malignant transformation of lung tissue and the leading cause of cancer-related deaths. The majority of cases are associated with long-term smoking. The disease is generally classified histologically as either small cell lung cancer or non-small cell lung cancer. Symptoms include cough, dyspnea, weight loss, and chest discomfort. Lung Cancer, breast cancer Breast cancer Breast cancer is a disease characterized by malignant transformation of the epithelial cells of the breast. Breast cancer is the most common form of cancer and 2nd most common cause of cancer-related death among women. Breast Cancer)
• Demyelinating disorders Demyelinating disorders Conditions characterized by loss or dysfunction of myelin in the brain, spinal cord, or optic nerves secondary to autoimmune mediated processes. This may take the form of a humoral or cellular immune response directed toward myelin or oligodendroglia associated autoantigens. Posterior Cord Syndrome:
  • Multiple sclerosis Sclerosis A pathological process consisting of hardening or fibrosis of an anatomical structure, often a vessel or a nerve. Wilms Tumor
  • Acute demyelinating encephalomyelitis
  • Guillain-Barré syndrome Guillain-Barré syndrome Guillain-Barré syndrome (GBS), once thought to be a single disease process, is a family of immune-mediated polyneuropathies that occur after infections (e.g., with Campylobacter jejuni). Guillain-Barré Syndrome
  • Tolosa-Hunt syndrome
  • Sarcoidosis Sarcoidosis Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Sarcoidosis
  • Systemic lupus erythematosus Systemic lupus erythematosus Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus ( SLE SLE Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus)
• Epilepsy Epilepsy Epilepsy is a chronic brain disorder marked by recurrent and unprovoked seizures. These seizures can be classified as focal or generalized and idiopathic or secondary to another condition. Clinical presentation correlates to the classification of the epileptic disorder. Epilepsy: focal seizures Focal Seizures Seizures in Children

Clinical presentation

Diagnosis

• Based on history and physical examination
• Imaging: CT/MRI to determine the presence of cerebrovascular events or tumors

Management

• Medical therapy:
  • 1st line: carbamazepine Carbamazepine A dibenzazepine that acts as a sodium channel blocker. It is used as an anticonvulsant for the treatment of grand mal and psychomotor or focal seizures. It may also be used in the management of bipolar disorder, and has analgesic properties. First-Generation Anticonvulsant Drugs
  • 2nd line: oxcarbazepine Oxcarbazepine A carbamazepine derivative that acts as a voltage-gated sodium channel blocker. It is used for the treatment of partial seizures with or without secondary generalization. It is also an inducer of cytochrome p-450 cyp3a4. First-Generation Anticonvulsant Drugs, gabapentin Gabapentin A cyclohexane-gamma-aminobutyric acid derivative that is used for the treatment of partial seizures; neuralgia; and restless legs syndrome. Second-Generation Anticonvulsant Drugs, phenytoin Phenytoin An anticonvulsant that is used to treat a wide variety of seizures. The mechanism of therapeutic action is not clear, although several cellular actions have been described including effects on ion channels, active transport, and general membrane stabilization. Phenytoin has been proposed for several other therapeutic uses, but its use has been limited by its many adverse effects and interactions with other drugs. First-Generation Anticonvulsant Drugs
• Surgical therapy: indicated when medical therapy is ineffective or not tolerated

Differential diagnoses

• Cluster headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
• Sphenoid sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis
• Temporal arteritis Temporal arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis ( giant cell arteritis Giant Cell Arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis)
• Postherpetic neuralgia Postherpetic neuralgia Pain in nerves, frequently involving facial skin, resulting from the activation the latent varicella-zoster virus. The two forms of the condition preceding the pain are herpes zoster oticus; and herpes zoster ophthalmicus. Following the healing of the rashes and blisters, the pain sometimes persists. Herpes Zoster (Shingles)
• Glossopharyngeal neuralgia

Cranial Nerve VI (Abducens) Palsy

Epidemiology

• Most commonly affected ocular nerve in adults
• 2nd-most common palsy in children
• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 2.5 cases per 100,000 individuals
• Uncontrolled type 2 Type 2 Spinal Muscular Atrophy diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus is a prominent risk factor.

Etiology

• Orbital neoplasia
• Trauma
• Ischemic stroke Ischemic Stroke An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke of the pons Pons The front part of the hindbrain (rhombencephalon) that lies between the medulla and the midbrain (mesencephalon) ventral to the cerebellum. It is composed of two parts, the dorsal and the ventral. The pons serves as a relay station for neural pathways between the cerebellum to the cerebrum. Brain Stem: Anatomy
• Wernicke disease
• SLE SLE Systemic lupus erythematosus (SLE) is a chronic autoimmune, inflammatory condition that causes immune-complex deposition in organs, resulting in systemic manifestations. Women, particularly those of African American descent, are more commonly affected. Systemic Lupus Erythematosus
• Aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms that compromises its trajectory
• Giant cell arteritis Giant Cell Arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis ( temporal arteritis Temporal arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis)
• Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease:
  • Lyme disease Lyme disease Lyme disease is a tick-borne infection caused by the gram-negative spirochete Borrelia burgdorferi. Lyme disease is transmitted by the black-legged Ixodes tick (known as a deer tick), which is only found in specific geographic regions. Patient presentation can vary depending on the stage of the disease and may include a characteristic erythema migrans rash. Lyme Disease
  • Syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis
  • TB TB Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis
  • Cryptococcosis Cryptococcosis Cryptococcosis is an opportunistic, fungal infection caused by the Cryptococcus species. The principal pathogens in humans are C. neoformans (primary) and C. gattii. The majority of affected patients are immunocompromised. Patients with AIDS, chronic steroid use, and organ transplant are particularly affected. Cryptococcosis is an AIDS-defining illness and typically associated with CD4 count < 100 cells/μL. Cryptococcus/Cryptococcosis
• Complication of:
  • Otitis media
  • Mastoiditis Mastoiditis Inflammation of the honeycomb-like mastoid bone in the skull just behind the ear. It is usually a complication of otitis media. Mumps Virus/Mumps
  • Basal skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull: Anatomy fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures
• Iatrogenic Iatrogenic Any adverse condition in a patient occurring as the result of treatment by a physician, surgeon, or other health professional, especially infections acquired by a patient during the course of treatment. Anterior Cord Syndrome (e.g., post-lumbar puncture)

Pathophysiology

• Longest intracranial path for any CN
• Ipsilateral supply to the lateral rectus Lateral rectus Orbit and Extraocular Muscles: Anatomy (sole innervation for this muscle)
• Allows abduction Abduction Examination of the Upper Limbs to occur
• Disruption of the nerve leads to weakness or paralysis of the ipsilateral lateral rectus Lateral rectus Orbit and Extraocular Muscles: Anatomy → inability to properly abduct the eye and inability in inward deviation

Clinical presentation

• Horizontal binocular diplopia Diplopia A visual symptom in which a single object is perceived by the visual cortex as two objects rather than one. Disorders associated with this condition include refractive errors; strabismus; oculomotor nerve diseases; trochlear nerve diseases; abducens nerve diseases; and diseases of the brain stem and occipital lobe. Myasthenia Gravis resulting in compensatory head turning
• Weak abduction Abduction Examination of the Upper Limbs of the affected eye

Diagnosis

• Based on history and physical examination
• Additional studies depend on suspected etiology:
  • Labs:
    • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus: serum glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance, HbA1c HbA1c Products of non-enzymatic reactions between glucose and hemoglobin a, occurring as a minor fraction of the hemoglobin components of human erythrocytes. Hemoglobin a1c is hemoglobin a with glucose covalently bound to the terminal valine of the beta chain. Glycated hemoglobin a is used as an index of the average blood sugar level over a lifetime of erythrocytes. Diabetes Mellitus
    • Syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis: rapid plasma reagin test Rapid plasma reagin test Treponema and VDRL VDRL Treponema
  • Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant (CT/MRI): trauma, ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage, aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms, neoplasm
  • Diagnostic lumbar puncture Lumbar Puncture Febrile Infant: increased intracranial pressure Intracranial Pressure Idiopathic Intracranial Hypertension ( ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP))

Management

• For pediatric subjects:
  • Alternate patching
  • Prism therapy
  • Strabismus Strabismus Strabismus is the misalignment of the eyes while fixating the gaze on an object. Strabismus can be idiopathic, but it may also be caused by cerebral palsy, uncorrected refractive errors, and extraocular muscle or cranial nerve dysfunction. Strabismus surgery in nonresponsive cases
• Conservative:
  • Observation: The majority of cases are self-limiting Self-Limiting Meningitis in Children.
  • Steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors to treat giant cell arteritis Giant Cell Arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis
  • Botulinum toxin Botulinum toxin Toxic proteins produced from the species Clostridium botulinum. The toxins are synthesized as a single peptide chain which is processed into a mature protein consisting of a heavy chain and light chain joined via a disulfide bond. The botulinum toxin light chain is a zinc-dependent protease which is released from the heavy chain upon endocytosis into presynaptic nerve endings. Once inside the cell the botulinum toxin light chain cleaves specific snare proteins which are essential for secretion of acetylcholine by synaptic vesicles. This inhibition of acetylcholine release results in muscular paralysis. Botulism injection into the overactive medial rectus Medial rectus Orbit and Extraocular Muscles: Anatomy muscle
• Surgical:
  • In cases of increased ICP Increased ICP Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage, aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms, or neoplasm
  • Procedures may include:
    • Decompressive craniectomy Decompressive Craniectomy Excision of part of the skull. This procedure is used to treat elevated intracranial pressure that is unresponsive to conventional treatment. Neurosurgery/ craniotomy Craniotomy Surgical incision into the cranium. Neurosurgery
    • Therapeutic lumbar puncture Lumbar Puncture Febrile Infant

Differential diagnoses

• Myasthenia gravis Myasthenia Gravis Myasthenia gravis (MG) is an autoimmune neuromuscular disorder characterized by weakness and fatigability of skeletal muscles caused by dysfunction/destruction of acetylcholine receptors at the neuromuscular junction. MG presents with fatigue, ptosis, diplopia, dysphagia, respiratory difficulties, and progressive weakness in the limbs, leading to difficulty in movement. Myasthenia Gravis
• TAO TAO A non-atherosclerotic, inflammatory thrombotic disease that commonly involves small and medium-sized arteries or veins in the extremities. It is characterized by occlusive thrombosis and fibrosis in the vascular wall leading to digital and limb ischemia and ulcerations. Thromboangiitis obliterans is highly associated with tobacco smoking. Thromboangiitis Obliterans (Buerger’s Disease)
• Idiopathic Idiopathic Dermatomyositis intracranial hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension ( pseudotumor cerebri Pseudotumor cerebri Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a clinical disorder that presents with symptoms due to increased intracranial pressure (ICP; ≥ 20 mm hg) or CSF pressure (> 250 mm H2O), with no structural changes or other attributable causes. Idiopathic Intracranial Hypertension)

Cranial Nerve VII (Facial) Palsy

Etiology

• Idiopathic Idiopathic Dermatomyositis (70% of cases of facial palsy account for Bell palsy ( lower motor neuron Lower Motor Neuron Motor Neuron Lesions))
• Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease:
  • HSV HSV Herpes simplex virus (HSV) is a double-stranded DNA virus belonging to the family Herpesviridae. Herpes simplex virus commonly causes recurrent infections involving the skin and mucosal surfaces, including the mouth, lips, eyes, and genitals. Herpes Simplex Virus 1 and 2 (Ramsay-Hunt syndrome)
  • EBV EBV Epstein-barr virus (EBV) is a linear, double-stranded DNA virus belonging to the herpesviridae family. This highly prevalent virus is mostly transmitted through contact with oropharyngeal secretions from an infected individual. The virus can infect epithelial cells and B lymphocytes, where it can undergo lytic replication or latency. Epstein-Barr Virus
  • Cytomegalovirus Cytomegalovirus CMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus
  • Adenovirus Adenovirus Adenovirus (member of the family Adenoviridae) is a nonenveloped, double-stranded DNA virus. Adenovirus is transmitted in a variety of ways, and it can have various presentations based on the site of entry. Presentation can include febrile pharyngitis, conjunctivitis, acute respiratory disease, atypical pneumonia, and gastroenteritis. Adenovirus
  • Rubella Rubella An acute infectious disease caused by the rubella virus. The virus enters the respiratory tract via airborne droplet and spreads to the lymphatic system. Rubella Virus virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology
  • Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza B virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology
  • Coxsackievirus Coxsackievirus Coxsackievirus is a member of a family of viruses called Picornaviridae and the genus Enterovirus. Coxsackieviruses are single-stranded, positive-sense RNA viruses, and are divided into coxsackie group A and B viruses. Both groups of viruses cause upper respiratory infections, rashes, aseptic meningitis, or encephalitis. Coxsackievirus
  • HIV HIV Anti-HIV Drugs
  • Lyme disease Lyme disease Lyme disease is a tick-borne infection caused by the gram-negative spirochete Borrelia burgdorferi. Lyme disease is transmitted by the black-legged Ixodes tick (known as a deer tick), which is only found in specific geographic regions. Patient presentation can vary depending on the stage of the disease and may include a characteristic erythema migrans rash. Lyme Disease
• Trauma
• Stroke
• Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus mellitus
• Parotid gland Parotid gland The largest of the three pairs of salivary glands. They lie on the sides of the face immediately below and in front of the ear. Salivary Glands: Anatomy pathology ( tumor Tumor Inflammation, inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation, sarcoidosis Sarcoidosis Sarcoidosis is a multisystem inflammatory disease that causes noncaseating granulomas. The exact etiology is unknown. Sarcoidosis usually affects the lungs and thoracic lymph nodes, but it can also affect almost every system in the body, including the skin, heart, and eyes, most commonly. Sarcoidosis)
• Pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
• Guillain-Barré syndrome Guillain-Barré syndrome Guillain-Barré syndrome (GBS), once thought to be a single disease process, is a family of immune-mediated polyneuropathies that occur after infections (e.g., with Campylobacter jejuni). Guillain-Barré Syndrome

Pathophysiology

• Facial nerve palsy Facial Nerve Palsy Lyme Disease is the inability to use the muscles of facial expression Muscles of facial expression The facial muscles (also called mimetic muscles) control facial expression and are supplied by the facial nerve. Most of them originate from the skull and attach to the skin around the facial openings, which serve as a method to group or classify them. Facial Muscles: Anatomy.
• Divided into upper and lower motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology deficiencies:
  • Upper motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology neuron deficiency (central palsy):
    • Originates from the cortex to the pons Pons The front part of the hindbrain (rhombencephalon) that lies between the medulla and the midbrain (mesencephalon) ventral to the cerebellum. It is composed of two parts, the dorsal and the ventral. The pons serves as a relay station for neural pathways between the cerebellum to the cerebrum. Brain Stem: Anatomy (brainstem)
    • Supplies the contralateral facial muscles Facial muscles The facial muscles (also called mimetic muscles) control facial expression and are supplied by the facial nerve. Most of them originate from the skull and attach to the skin around the facial openings, which serve as a method to group or classify them. Facial Muscles: Anatomy
    • Supplies BOTH upper facial muscles Facial muscles The facial muscles (also called mimetic muscles) control facial expression and are supplied by the facial nerve. Most of them originate from the skull and attach to the skin around the facial openings, which serve as a method to group or classify them. Facial Muscles: Anatomy (eyes and forehead Forehead The part of the face above the eyes. Melasma); therefore, single-sided lesions still spare the forehead Forehead The part of the face above the eyes. Melasma and eye muscles
  • Lower motor neuron Lower Motor Neuron Motor Neuron Lesions deficiency (peripheral palsy):
    • Originates from the nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles in the pons Pons The front part of the hindbrain (rhombencephalon) that lies between the medulla and the midbrain (mesencephalon) ventral to the cerebellum. It is composed of two parts, the dorsal and the ventral. The pons serves as a relay station for neural pathways between the cerebellum to the cerebrum. Brain Stem: Anatomy and branches into several nerves to muscles in the face
    • Supplies the ipsilateral facial muscles Facial muscles The facial muscles (also called mimetic muscles) control facial expression and are supplied by the facial nerve. Most of them originate from the skull and attach to the skin around the facial openings, which serve as a method to group or classify them. Facial Muscles: Anatomy
• Other functions of the nerve include:
  • Taste from the anterior ⅔ of the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy ( chorda tympani Chorda tympani A branch of the facial (7th cranial) nerve which passes through the middle ear and continues through the petrotympanic fissure. The chorda tympani nerve carries taste sensation from the anterior two-thirds of the tongue and conveys parasympathetic efferents to the salivary glands. Lips and Tongue: Anatomy)
  • Lacrimation
  • Salivation
  • Auditory reflex

Clinical presentation

• Upper motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology lesion:
  • Mouth is drooped (suggests contralateral lesion).
  • The eye can be closed, frown intact
• Lower motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology lesion:
  • Complete facial paralysis on 1 side (same side as the lesion)
  • Eyes cannot be closed.
  • No frown
  • Mouth drooped and drooling Drooling Peritonsillar Abscess
• Peripheral nerve damage:
  • Hyperacusis (sensitivity to loud noises)
  • Loss of taste in the anterior ⅔ of the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy
  • Decreased lacrimation → ocular ulceration Ulceration Corneal Abrasions, Erosion, and Ulcers/ keratitis Keratitis Inflammation of the cornea. Herpes Simplex Virus 1 and 2
  • Uneven salivation

Diagnosis

• Based on history and physical examination
• Assessment of facial palsy using the House-Brackman grading Grading Methods which attempt to express in replicable terms the level of cell differentiation in neoplasms as increasing anaplasia correlates with the aggressiveness of the neoplasm. Grading, Staging, and Metastasis system
• Evoke reflexes:
  • Corneal
  • Stapedius
• Ear exam may show cutaneous vesicles Vesicles Female Genitourinary Examination if Ramsay-Hunt syndrome is present.
• Lacrimation: Schirmer test
• Audiogram

Management

• Therapeutic goal: restoration of facial motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility
• Medical:
  • Prednisolone Prednisolone A glucocorticoid with the general properties of the corticosteroids. It is the drug of choice for all conditions in which routine systemic corticosteroid therapy is indicated, except adrenal deficiency states. Immunosuppressants
  • Ramsay-Hunt syndrome: acyclovir Acyclovir A guanosine analog that acts as an antimetabolite. Viruses are especially susceptible. Used especially against herpes. Herpes Zoster (Shingles) and analgesia Analgesia Methods of pain relief that may be used with or in place of analgesics. Anesthesiology: History and Basic Concepts ( acetaminophen Acetaminophen Acetaminophen is an over-the-counter nonopioid analgesic and antipyretic medication and the most commonly used analgesic worldwide. Despite the widespread use of acetaminophen, its mechanism of action is not entirely understood. Acetaminophen or ibuprofen Ibuprofen A nonsteroidal anti-inflammatory agent with analgesic properties used in the treatment of rheumatism and arthritis. Nonsteroidal Antiinflammatory Drugs (NSAIDs))
• Physical therapy Physical Therapy Becker Muscular Dystrophy: facial exercises
• Surgical: facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions decompression
• Incomplete closure of the eye: urgent ophthalmology consultation and eye protection to avoid corneal damage

Differential diagnoses

• Ischemic and hemorrhagic stroke Hemorrhagic stroke Stroke due to rupture of a weakened blood vessel in the brain (e.g., cerebral hemispheres; cerebellum; subarachnoid space). Subarachnoid Hemorrhage
• Acute otitis media Acute Otitis Media Acute otitis media is an infection in the middle ear characterized by mucosal inflammation and retention of fluid. The most common pathogens are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The condition can present with fever, otalgia, and diminished hearing. Acute Otitis Media

Cranial Nerve VIII (Vestibulocochlear) Palsy

Epidemiology

• Decreased hearing acuity has a lifetime prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency in approximately 10% of the general population.
• Tinnitus has a lifetime prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency in approximately 30% of the general population.
• Dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome)/ vertigo Vertigo Vertigo is defined as the perceived sensation of rotational motion while remaining still. A very common complaint in primary care and the ER, vertigo is more frequently experienced by women and its prevalence increases with age. Vertigo is classified into peripheral or central based on its etiology. Vertigo has a lifetime prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency in approximately 20% of the general population.

Etiology

• Congenital Congenital Chorioretinitis abnormalities:
  • Aplasia
  • Hypoplasia Hypoplasia Hypoplastic Left Heart Syndrome (HLHS)
• Tumor Tumor Inflammation:
  • Acoustic neuroma Acoustic neuroma Acoustic neuroma, also referred to as vestibular schwannoma, is a benign tumor arising from Schwann cells of the vestibular component of the cranial nerve VIII. Acoustic neuroma forms within the internal auditory meatus and extends into the cerebellopontine angle. Acoustic Neuroma
  • Neurofibromatosis type-2
• Trauma to the temporal bone Temporal bone Either of a pair of compound bones forming the lateral (left and right) surfaces and base of the skull which contains the organs of hearing. It is a large bone formed by the fusion of parts: the squamous (the flattened anterior-superior part), the tympanic (the curved anterior-inferior part), the mastoid (the irregular posterior portion), and the petrous (the part at the base of the skull). Jaw and Temporomandibular Joint: Anatomy or bony labyrinth
• Infection
• Ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage/infarction
• Demyelination Demyelination Multiple Sclerosis (multiple sclerosis Sclerosis A pathological process consisting of hardening or fibrosis of an anatomical structure, often a vessel or a nerve. Wilms Tumor)
• Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation ( vestibular neuritis Vestibular neuritis Idiopathic inflammation of the vestibular nerve, characterized clinically by the acute or subacute onset of vertigo; nausea; and imbalance. The cochlear nerve is typically spared and hearing loss and tinnitus do not usually occur. Symptoms usually resolve over a period of days to weeks. Vertigo)
• Drugs

Pathophysiology

General physiology:

• CN VIII contains “special” afferent Afferent Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology fibers that carry the senses of hearing and balance.
• Consists of the vestibular and cochlear nerves:
  • 2 distinct nuclei in the brainstem
  • Cochlear nerve plays a role in hearing.
  • Vestibular nerve plays a role in maintaining equilibrium Equilibrium Occurs when tumor cells survive the initial elimination attempt These cells are not able to progress, being maintained in a state of dormancy by the adaptive immune system. In this phase, tumor immunogenicity is edited, where T cells keep selectively attacking highly immunogenic tumor cells.This attack leaves other cells with less immunogenicity to potentially develop resistance to the immune response. Cancer Immunotherapy/balance and extraocular movements.

Cochlear nerve:

The cochlear nerve transmits sound stimuli from the inner ear Inner ear The essential part of the hearing organ consists of two labyrinthine compartments: the bony labyrinthine and the membranous labyrinth. Ear: Anatomy (fluid-filled cochlea Cochlea The part of the inner ear (labyrinth) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the vestibular labyrinth. Ear: Anatomy) to the cochlear nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles (brainstem) and then to the primary auditory cortex Auditory cortex The region of the cerebral cortex that receives the auditory radiation from the medial geniculate body. Auditory and Vestibular Pathways: Anatomy ( temporal lobe Temporal lobe Lower lateral part of the cerebral hemisphere responsible for auditory, olfactory, and semantic processing. It is located inferior to the lateral fissure and anterior to the occipital lobe. Cerebral Cortex: Anatomy).

• Neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology that sense peripheral sounds ( hair cells Hair cells Auditory sensory cells of organ of corti, usually placed in one row medially to the core of spongy bone (the modiolus). Inner hair cells are in fewer numbers than the outer auditory hair cells, and their stereocilia are approximately twice as thick as those of the outer hair cells. Auditory and Vestibular Pathways: Anatomy) are contained in the fluid-filled cochlea Cochlea The part of the inner ear (labyrinth) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the vestibular labyrinth. Ear: Anatomy of the inner ear Inner ear The essential part of the hearing organ consists of two labyrinthine compartments: the bony labyrinthine and the membranous labyrinth. Ear: Anatomy.
• These neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology send projections centrally to become the cochlear nerve, which travels through the internal auditory canal to join the vestibular nerve (forming CN VIII) on its path to the brainstem.
• Upon entering the brainstem at the cerebellopontine angle Cerebellopontine angle Junction between the cerebellum and the pons. Acoustic Neuroma, the nerves again separate, with the cochlear nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology synapsing in the anteroventral, dorsal, and posteroventral cochlear nuclei.
• After synapsing at the cochlear nuclei, neurons Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the nervous system. Nervous System: Histology cross over to join the contralateral lateral lemniscus Lateral lemniscus Auditory and Vestibular Pathways: Anatomy toward the inferior colliculus Inferior colliculus The posterior pair of the quadrigeminal bodies which contain centers for auditory function. Brain Stem: Anatomy of the midbrain Midbrain The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the pons and the diencephalon. Midbrain contains two major parts, the dorsal tectum mesencephali and the ventral tegmentum mesencephali, housing components of auditory, visual, and other sensorimotor systems. Brain Stem: Anatomy and then project to the thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy (medial geniculate nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles) before reaching the primary auditory cortex Auditory cortex The region of the cerebral cortex that receives the auditory radiation from the medial geniculate body. Auditory and Vestibular Pathways: Anatomy.

Vestibular nerve:

• Vestibular nerve relays sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology information regarding motion and body position by coordinating inputs from the vestibular apparatus ( semicircular canals Semicircular canals Three long canals (anterior, posterior, and lateral) of the bony labyrinth. They are set at right angles to each other and are situated posterosuperior to the vestibule of the bony labyrinth (vestibular labyrinth). The semicircular canals have five openings into the vestibule with one shared by the anterior and the posterior canals. Within the canals are the semicircular ducts. Auditory and Vestibular Pathways: Anatomy, saccule Saccule A membranous sac within the vestibular labyrinth of the inner ear. The saccule communicates with cochlear duct through the ductus reuniens, and communicates with utricle through the utriculosaccular duct from which the endolymphatic duct arises. The utricle and saccule have sensory areas (acoustic maculae) which are innervated by the vestibular nerve. Auditory and Vestibular Pathways: Anatomy, and utricle Utricle A membranous sac within the vestibular labyrinth of the inner ear. The utricle communicates with the saccule through the utriculosaccular duct from which the endolymphatic duct arises. The utricle and saccule have sensory areas (acoustic maculae) which are innervated by the vestibular nerve. Auditory and Vestibular Pathways: Anatomy), extraocular muscles, postural muscles, brainstem, and cerebral cortex Cerebral cortex The cerebral cortex is the largest and most developed part of the human brain and CNS. Occupying the upper part of the cranial cavity, the cerebral cortex has 4 lobes and is divided into 2 hemispheres that are joined centrally by the corpus callosum. Cerebral Cortex: Anatomy.
• Components of the vestibular apparatus (all lined with sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology containing hair cells Hair cells Auditory sensory cells of organ of corti, usually placed in one row medially to the core of spongy bone (the modiolus). Inner hair cells are in fewer numbers than the outer auditory hair cells, and their stereocilia are approximately twice as thick as those of the outer hair cells. Auditory and Vestibular Pathways: Anatomy):
  • Utricle Utricle A membranous sac within the vestibular labyrinth of the inner ear. The utricle communicates with the saccule through the utriculosaccular duct from which the endolymphatic duct arises. The utricle and saccule have sensory areas (acoustic maculae) which are innervated by the vestibular nerve. Auditory and Vestibular Pathways: Anatomy: detects horizontal movement of the head
  • Saccule Saccule A membranous sac within the vestibular labyrinth of the inner ear. The saccule communicates with cochlear duct through the ductus reuniens, and communicates with utricle through the utriculosaccular duct from which the endolymphatic duct arises. The utricle and saccule have sensory areas (acoustic maculae) which are innervated by the vestibular nerve. Auditory and Vestibular Pathways: Anatomy: detects vertical movement of the head
  • 3 semicircular ducts (within the semicircular canals Semicircular canals Three long canals (anterior, posterior, and lateral) of the bony labyrinth. They are set at right angles to each other and are situated posterosuperior to the vestibule of the bony labyrinth (vestibular labyrinth). The semicircular canals have five openings into the vestibule with one shared by the anterior and the posterior canals. Within the canals are the semicircular ducts. Auditory and Vestibular Pathways: Anatomy): detect angular and rotary movements of the head
• Nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology project from the sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology to the vestibular ganglion in the internal auditory canal, which then joins the cochlear nerve (to form CN VII) on its path to the brainstem.
• Upon entering the brainstem at the cerebellopontine angle Cerebellopontine angle Junction between the cerebellum and the pons. Acoustic Neuroma, the nerves again separate, with vestibular nerve fibers Nerve Fibers Slender processes of neurons, including the axons and their glial envelopes (myelin sheath). Nerve fibers conduct nerve impulses to and from the central nervous system. Nervous System: Histology synapsing in the medial, lateral, superior, and inferior vestibular nuclei Vestibular nuclei The four cellular masses in the floor of the fourth ventricle giving rise to a widely dispersed special sensory system. Included is the superior, medial, inferior, and lateral vestibular nucleus. Vertigo:
  • Medial nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles helps mediate the vestibulo-ocular and vestibulospinal reflexes by contributing to the control of head and neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess movements.
  • Superior nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles helps mediate the vestibulo-ocular reflex.
  • Lateral nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles joins the fibers of the cerebellum Cerebellum The cerebellum, Latin for “little brain,” is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum: Anatomy to become the lateral vestibular tract within the ipsilateral spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy to mediate the vestibulospinal reflex and help maintain posture and balance.
  • Inferior nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles coordinates communication Communication The exchange or transmission of ideas, attitudes, or beliefs between individuals or groups. Decision-making Capacity and Legal Competence between the other 3 vestibular nuclei Vestibular nuclei The four cellular masses in the floor of the fourth ventricle giving rise to a widely dispersed special sensory system. Included is the superior, medial, inferior, and lateral vestibular nucleus. Vertigo and the cerebellum Cerebellum The cerebellum, Latin for “little brain,” is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum: Anatomy.

Vestibulocochlear nerve Vestibulocochlear nerve The 8th cranial nerve. The vestibulocochlear nerve has a cochlear part (cochlear nerve) which is concerned with hearing and a vestibular part (vestibular nerve) which mediates the sense of balance and head position. The fibers of the cochlear nerve originate from neurons of the spiral ganglion and project to the cochlear nuclei (cochlear nucleus). The fibers of the vestibular nerve arise from neurons of scarpa’s ganglion and project to the vestibular nuclei. The 12 Cranial Nerves: Overview and Functions injuries:

Injuries to the cochlear nerve often occur in either:

• Internal acoustic meatus or
• At the cerebellopontine angle Cerebellopontine angle Junction between the cerebellum and the pons. Acoustic Neuroma

Clinical presentation

• Tinnitus
• Sensorineural hearing loss Sensorineural hearing loss Hearing loss resulting from damage to the cochlea and the sensorineural elements which lie internally beyond the oval and round windows. These elements include the auditory nerve and its connections in the brainstem. Hearing Loss
• Impairment in equilibrium Equilibrium Occurs when tumor cells survive the initial elimination attempt These cells are not able to progress, being maintained in a state of dormancy by the adaptive immune system. In this phase, tumor immunogenicity is edited, where T cells keep selectively attacking highly immunogenic tumor cells.This attack leaves other cells with less immunogenicity to potentially develop resistance to the immune response. Cancer Immunotherapy/balance
• Vertigo Vertigo Vertigo is defined as the perceived sensation of rotational motion while remaining still. A very common complaint in primary care and the ER, vertigo is more frequently experienced by women and its prevalence increases with age. Vertigo is classified into peripheral or central based on its etiology. Vertigo
• Nystagmus Nystagmus Involuntary movements of the eye that are divided into two types, jerk and pendular. Jerk nystagmus has a slow phase in one direction followed by a corrective fast phase in the opposite direction, and is usually caused by central or peripheral vestibular dysfunction. Pendular nystagmus features oscillations that are of equal velocity in both directions and this condition is often associated with visual loss early in life. Albinism

Diagnosis

• Clinical evaluation:
  • Weber test
  • Rinne test
  • Romberg test Romberg Test Vertigo
• Audiologic testing
• Dix-Hallpike test
• Labs:
  • CBC
  • ESR ESR Soft Tissue Abscess
• Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant (of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and inner ear Inner ear The essential part of the hearing organ consists of two labyrinthine compartments: the bony labyrinthine and the membranous labyrinth. Ear: Anatomy):
  • CT for evaluation of bony structures
  • MRI (with contrast) for evaluation of soft tissue Soft Tissue Soft Tissue Abscess structures

Management

• Head, eyes, ears, nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose Anatomy (External & Internal), throat Throat The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx: Anatomy (HEENT), audiology, and neurology consultation as appropriate
• Neurosurgical consultation for tumors
• Hearing aids AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS for those with decreased hearing acuity
• Antiemetics Antiemetics Antiemetics are medications used to treat and/or prevent nausea and vomiting. These drugs act on different target receptors. The main classes include benzodiazepines, corticosteroids, atypical antipsychotics, cannabinoids, and antagonists of the following receptors: serotonin, dopamine, and muscarinic and neurokinin receptors. Antiemetics, meclizine Meclizine A histamine h1 antagonist used in the treatment of motion sickness, vertigo, and nausea during pregnancy and radiation sickness. Antihistamines for vertigo Vertigo Vertigo is defined as the perceived sensation of rotational motion while remaining still. A very common complaint in primary care and the ER, vertigo is more frequently experienced by women and its prevalence increases with age. Vertigo is classified into peripheral or central based on its etiology. Vertigo
• Steroid burst and taper may be useful in inflammatory conditions.

Differential diagnoses

• Psychosis
• Ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage/infarction

Cranial Nerve IX (Glossopharyngeal) Palsy

Etiology

• Head, neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, and oral trauma
• Glossopharyngeal neuralgia (very rare)
• Tumor Tumor Inflammation of the posterior fossa (conjunction with CN X and XI palsies)
• Iatrogenic Iatrogenic Any adverse condition in a patient occurring as the result of treatment by a physician, surgeon, or other health professional, especially infections acquired by a patient during the course of treatment. Anterior Cord Syndrome injury (e.g., laryngeal mask placement, surgery)
• Complication of tonsillectomy Tonsillectomy Surgical removal of a tonsil or tonsils. Tonsillitis
• Vernet syndrome
• Collet-Sicard syndrome
• Villaret syndrome
• Styloid fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures

Pathophysiology

• Injury to the nerve produces motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology and sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology deficits in its territory and discontinuity of reflex arcs.
• Motor deficit Motor Deficit Anterior Cord Syndrome is expressed as dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia.
• Sensory deficit Sensory Deficit Anterior Cord Syndrome is expressed as a reduced sense of taste in the posterior 3rd of the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy, palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Palate: Anatomy, and pharynx Pharynx The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx: Anatomy.
• Gag and carotid sinus Carotid sinus The dilated portion of the common carotid artery at its bifurcation into external and internal carotids. It contains baroreceptors which, when stimulated, cause slowing of the heart, vasodilatation, and a fall in blood pressure. Carotid Arterial System: Anatomy reflexes are abolished, which manifest as the inability to evoke emesis and protect the airway Airway ABCDE Assessment (increased risk of aspiration), and regulate blood pressure ( syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope), respectively.

Clinical presentation

• Dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia
• Absent gag reflex
• Reduced sensation over the posterior 3rd of the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy, palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Palate: Anatomy, and pharynx Pharynx The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx: Anatomy
• Loss of carotid sinus Carotid sinus The dilated portion of the common carotid artery at its bifurcation into external and internal carotids. It contains baroreceptors which, when stimulated, cause slowing of the heart, vasodilatation, and a fall in blood pressure. Carotid Arterial System: Anatomy reflex → orthostasis/ syncope Syncope Syncope is a short-term loss of consciousness and loss of postural stability followed by spontaneous return of consciousness to the previous neurologic baseline without the need for resuscitation. The condition is caused by transient interruption of cerebral blood flow that may be benign or related to a underlying life-threatening condition. Syncope
• Dysfunction of parotid gland Parotid gland The largest of the three pairs of salivary glands. They lie on the sides of the face immediately below and in front of the ear. Salivary Glands: Anatomy secretion Secretion Coagulation Studies
• In cases of neuralgia:
  • Severe, sharp/stabbing pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways that lasts for seconds to a few minutes
  • Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways is exacerbated by coughing, yawning, swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility, or talking.
• Commonly accompanied by symptoms of CN X and XI palsies

Diagnosis

• Based on history and physical examination
• Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant: CT to determine the presence of cerebrovascular events or tumors

Management

• Similar to that of trigeminal neuralgia Trigeminal neuralgia Trigeminal neuralgia (TN) is an often chronic and recurring pain syndrome involving the sensory distribution of the trigeminal nerve (cranial nerve (CN) V). The pain is typically unilateral and described as an acute, sharp, electric-shock-like pain involving the maxillary or mandibular areas and often associated with spasm of facial muscles. Trigeminal Neuralgia:
  • 1st-line therapy options:
    • Carbamazepine Carbamazepine A dibenzazepine that acts as a sodium channel blocker. It is used as an anticonvulsant for the treatment of grand mal and psychomotor or focal seizures. It may also be used in the management of bipolar disorder, and has analgesic properties. First-Generation Anticonvulsant Drugs
    • Oxcarbazepine Oxcarbazepine A carbamazepine derivative that acts as a voltage-gated sodium channel blocker. It is used for the treatment of partial seizures with or without secondary generalization. It is also an inducer of cytochrome p-450 cyp3a4. First-Generation Anticonvulsant Drugs
  • Alternative agents:
    • Baclofen Baclofen A gamma-aminobutyric acid derivative that is a specific agonist of gaba-b receptors. It is used in the treatment of muscle spasticity, especially that due to spinal cord injuries. Its therapeutic effects result from actions at spinal and supraspinal sites, generally the reduction of excitatory transmission. Spasmolytics
    • Lamotrigine Lamotrigine A phenyltriazine compound, sodium and calcium channel blocker that is used for the treatment of seizures and bipolar disorder. Second-Generation Anticonvulsant Drugs
    • Gabapentin Gabapentin A cyclohexane-gamma-aminobutyric acid derivative that is used for the treatment of partial seizures; neuralgia; and restless legs syndrome. Second-Generation Anticonvulsant Drugs
• Admission and neurology consultation if several nerves are compromised

Differential diagnoses

• CN X palsy
• CN V palsy

Cranial Nerve X (Vagus) Palsy

Etiology

• Recent carotid or thyroid Thyroid The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland: Anatomy surgery
• Tumor Tumor Inflammation of the posterior fossa (conjunction with CN IX and XI palsies)

Clinical presentation

• Hoarseness Hoarseness An unnaturally deep or rough quality of voice. Parapharyngeal Abscess
• Dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia
• Regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD) into the nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose Anatomy (External & Internal)
• Oral examination:
  • Dropped arch of the soft palate Soft palate A movable fold suspended from the posterior border of the hard palate. The uvula hangs from the middle of the lower border. Palate: Anatomy
  • Deviation of the uvula Uvula A fleshy extension at the back of the soft palate that hangs above the opening of the throat. Peritonsillar Abscess away from the affected side

Diagnosis

• Based on history and physical examination
• Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant: CT/MRI to determine the presence of cerebrovascular events or tumors

Management

• Depends on the underlying cause
• Speech and swallow therapy

Differential diagnoses

• CN IX palsy
• CN XII palsy

Cranial Nerve XI (Spinal Accessory) Palsy

Etiology

• Iatrogenic Iatrogenic Any adverse condition in a patient occurring as the result of treatment by a physician, surgeon, or other health professional, especially infections acquired by a patient during the course of treatment. Anterior Cord Syndrome injury (most common):
  • Removal of neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess masses
  • Cosmetic surgery (e.g., facelift)
• Jugular foramen tumors:
  • Collet-Sicard syndrome
  • Vernet syndrome
• Penetrating trauma ( posterior triangle Posterior triangle Triangles of the Neck: Anatomy of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess)
• Tumor Tumor Inflammation of the posterior fossa (conjunction with CN XI and X palsies)
• Brachial neuritis
• Poliomyelitis Poliomyelitis Poliomyelitis is an infectious disease caused by the poliovirus. Transmission occurs through the fecal-oral route and through respiratory aerosols. The majority of patients will be asymptomatic or have a mild, abortive presentation with flu-like symptoms. Those who develop nonparalytic poliomyelitis will develop signs and symptoms of aseptic meningitis. A very minor proportion of patients will progress to paralytic poliomyelitis. Poliovirus/Poliomyelitis

Clinical presentation

• Shoulder pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and weakness
• Shoulder drooping
• Decreased ability to hold the shoulder in abduction Abduction Examination of the Upper Limbs
• Positive scapular flip sign:
  • Lateral scapular winging
  • Ipsilateral nerve damage ( lower motor neuron Lower Motor Neuron Motor Neuron Lesions)
• Compensatory traction and straining of the levator scapulae and rhomboid muscles
• Trapezius atrophy Atrophy Decrease in the size of a cell, tissue, organ, or multiple organs, associated with a variety of pathological conditions such as abnormal cellular changes, ischemia, malnutrition, or hormonal changes. Cellular Adaptation

Diagnosis

• Based on history and physical examination
• Electromyography Electromyography Recording of the changes in electric potential of muscle by means of surface or needle electrodes. Becker Muscular Dystrophy (EMG) can be used to determine the extent of palsy.
• High-resolution ultrasonography allows visualization of normal CN XI anatomy and may reveal anatomical changes after injury (i.e., loss of continuity, free nerve endings).

Management

• Specific therapeutic options depend on the etiology.
• Medical:
  • NSAIDs NSAIDS Primary vs Secondary Headaches
  • Nerve stimulation
  • Regional nerve block
  • PT and rehabilitation
• Surgical:
  • Nerve reanastomosis
  • Nerve grafting

Differential diagnoses

• Long thoracic nerve Long thoracic nerve Axilla and Brachial Plexus: Anatomy palsy
• Rotator cuff injury

Cranial Nerve XII (Hypoglossal) Palsy

Etiology

• Intracranial/skull-base tumors
• Vertebral trauma
• Internal carotid artery dissection Carotid artery dissection The splitting of the vessel wall in one or both (left and right) internal carotid arteries. Interstitial hemorrhage into the media of the vessel wall can lead to occlusion of the internal carotid artery and aneurysm formation. Dissection of the Carotid and Vertebral Arteries or aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms
• Pharyngeal space tumors
• Rare complication of airway Airway ABCDE Assessment management during general anesthesia General anesthesia Procedure in which patients are induced into an unconscious state through use of various medications so that they do not feel pain during surgery. Anesthesiology: History and Basic Concepts

Pathophysiology

• Compression Compression Blunt Chest Trauma/stretching of the nerve → injury
• Injury produces motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology deficits in its territory.

Clinical presentation

• Unilateral tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy weakness on the affected side
• Dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia
• Difficulty with speech

Diagnosis

• Based on history and physical examination
• Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant: CT/MRI to determine the presence of cerebrovascular events or tumors

Management

• Depends on the underlying cause
• Speech and swallow therapy