Cranial nerve palsy is a congenital Congenital Chorioretinitis or acquired dysfunction of 1 or more cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions that will, in turn, lead to focal neurologic abnormalities in movement or autonomic dysfunction Autonomic Dysfunction Anterior Cord Syndrome of its territory. Head/ neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess trauma, mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast effect, infectious Infectious Febrile Infant processes, and 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 are among the many etiologies for these dysfunctions. Diagnosis is initially clinical and supported by diagnostic 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. Management includes both symptomatic measures and interventions aimed at correcting the underlying cause.
Last updated: 30 Jun, 2022
Contents
The table below summarizes the functions of the 12 CNs.
CN | Name | Function | Type |
---|---|---|---|
I | Olfactory | 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 ( 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) | Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology |
II | Optic | Vision Vision Ophthalmic Exam | Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology |
III | Oculomotor |
|
Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology |
IV | Trochlear | Eye movement ( superior oblique Superior oblique Orbit and Extraocular Muscles: Anatomy muscle) | Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology |
V | Trigeminal |
|
Both |
VI | Abducens | Eye movement ( lateral rectus Lateral rectus Orbit and Extraocular Muscles: Anatomy muscle) | Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology |
VII | Facial |
|
Both |
VIII | Vestibulocochlear |
|
Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology |
IX | Glossopharyngeal |
|
Both |
X | Vagus |
|
Both |
XI | Accessory |
|
Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology |
XII | Hypoglossal | 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 movements | Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology |
Cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions
Image by Lecturio.Overview of the peripheral and central components of the olfactory system
Image by Lecturio.A closer look at the olfactory sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology cells 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, passing through the cribriform plate and synapsing with the olfactory tract Olfactory tract Olfaction: Anatomy at the olfactory bulbs
Image by Lecturio.Examination of cranial nerve I: presenting the subject with a familiar olfactory stimulus
Image by Lecturio.Diagram of the visual pathway Visual pathway The primary visual pathway consists of a relay system, beginning at the retina, whose ganglion cell axons form the optic nerve. The optic nerve fibers from each eye hemidecussate in the optic chiasm (OC), with nasal fibers joining the temporal fibers of the contralateral nerve. Signals are then transmitted to the primary visual cortex of the occipital lobe. The Visual Pathway and Related Disorders and the visual fields: Light enters the eye, sending signals to 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 and through 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. The nasal fibers of each eye decussate at 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, continuing to the 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 with the temporal fibers. The right nasal fibers join the left temporal fibers (blue lines) and the left nasal fibers join the right temporal fibers (red lines). 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 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 lateral 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. Optic radiations connect the lateral 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 to the primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy 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 where visual information is processed.
Image by Lecturio.Innervation of ocular muscles by cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. The 12 Cranial Nerves: Overview and Functions III, IV, and VI
Image by Lecturio.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 fixed and dilated in a position of lateral and downward (down-and-out) gaze
Image: “ 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 palsy” by Hakim W, Sherman R, Rezk T, Pannu K. License: CC BY 3.0Urgent:
Nonurgent:
Left
trochlear nerve
Trochlear nerve
The 4th cranial nerve. The trochlear nerve carries the motor innervation of the superior oblique muscles of the eye.
The 12 Cranial Nerves: Overview and Functions palsy:
The subject was asked to look right after looking left. The
left eye
Left Eye
Refractive Errors shows extortion.
Site of damage | Clinical findings | Other findings | Common causes |
---|---|---|---|
Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology cortex |
|
|
|
Internal capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides | Hemifacial sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology loss | Hemiparesis Hemiparesis The term hemiparesis refers to mild to moderate weakness involving one side of the body. Epidural Hemorrhage of the arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy |
|
Corona radiata | Central 7th cranial nerve paresis Paresis A general term referring to a mild to moderate degree of muscular weakness, occasionally used as a synonym for paralysis (severe or complete loss of motor function). In the older literature, paresis often referred specifically to paretic neurosyphilis. ‘general paresis’ and ‘general paralysis’ may still carry that connotation. Bilateral lower extremity paresis is referred to as paraparesis. Spinal Disk Herniation | ||
VPM 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 |
|
|
|
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 |
|
Ophthalmoparesis |
|
Site of damage | Clinical findings | Other findings | Common causes |
---|---|---|---|
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 |
|
|
|
Medulla |
|
|
|
Site of damage | Clinical findings | Other findings | Common causes |
---|---|---|---|
Cerebellopontine angle Cerebellopontine angle Junction between the cerebellum and the pons. Acoustic Neuroma | Facial numbness |
|
|
Gasserian ganglion | Facial numbness and weakness |
|
|
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 base | Facial numbness and weakness |
|
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 (bacterial, 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, cancer, sarcoid) |
Site of damage | Clinical findings | Other findings | Common causes |
---|---|---|---|
V1: cavernous sinus |
|
|
|
V1: carotid-cavernous fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula | Facial numbness |
|
Trauma |
V2: maxillary region |
|
|
|
V3: mandibular region |
|
|
A child with nephrotic syndrome Nephrotic syndrome Nephrotic syndrome is characterized by severe proteinuria, hypoalbuminemia, and peripheral edema. In contrast, the nephritic syndromes present with hematuria, variable loss of renal function, and hypertension, although there is sometimes overlap of > 1 glomerular disease in the same individual. Nephrotic Syndrome demonstrating typical nephrotic facial puffiness and right cranial nerve VI palsy: The patient is unable to abduct the right eye Right Eye Refractive Errors.
Image: “F0001” by Shalinee Bhoobun et al AL Amyloidosis. License: CC BY 2.0The nuclei of the
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 are in the brainstem.
Orange: nerves coming from the left hemisphere 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
Yellow: nerves coming from the right hemisphere 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
Individual with Bell palsy (lower
motor
Motor
Neurons which send impulses peripherally to activate muscles or secretory cells.
Nervous System: Histology lesion):
Drooped mouth and the inability to close the
left eye
Left Eye
Refractive Errors are noted.
Grade | Definition |
---|---|
I | Normal symmetrical Symmetrical Dermatologic Examination function throughout |
II |
|
III |
|
IV |
|
V |
|
VI |
|
Ear vesicles Vesicles Female Genitourinary Examination seen in Ramsay-Hunt syndrome
Image: “Erythème et vésicules cutanées de la zone de Ramsay Hunt droite” by Mahfoudhi M, Lahiani R. License: CC BY 2.0General physiology:
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).
Vestibular nerve:
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:
Structures innervated by cranial nerve X (vagus)
N. = nerve
R. = ramus
Rr
RR
Relative risk (RR) is the risk of a disease or condition occurring in a group or population with a particular exposure relative to a control (unexposed) group.
Measures of Risk. = rami
Right-sided vagal palsy: 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 on the right side, deviated uvula Uvula A fleshy extension at the back of the soft palate that hangs above the opening of the throat. Peritonsillar Abscess on the left
Image by Lecturio.Innervation of the sternocleidomastoid Sternocleidomastoid Muscles of the Neck: Anatomy and trapezius muscles by CN XI ( spinal accessory nerve Spinal accessory nerve The 11th cranial nerve which originates from neurons in the medulla and in the cervical spinal cord. It has a cranial root, which joins the vagus nerve (10th cranial) and sends motor fibers to the muscles of the larynx, and a spinal root, which sends motor fibers to the trapezius and the sternocleidomastoid muscles. The 12 Cranial Nerves: Overview and Functions)
Image by Lecturio.Positive scapular flip sign seen in cranial nerve XI (accessory) palsy
Image by Lecturio.Unilateral
hypoglossal nerve
Hypoglossal nerve
The 12th cranial nerve. The hypoglossal nerve originates in the hypoglossal nucleus of the medulla and supplies motor innervation to all of the muscles of the tongue except the palatoglossus (which is supplied by the vagus). This nerve also contains proprioceptive afferents from the tongue muscles.
Lips and Tongue: Anatomy palsy after using the LMA device:
(a): On postoperative day 1, 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 deviated to the right side on protrusion, demonstrating right
hypoglossal nerve
Hypoglossal nerve
The 12th cranial nerve. The hypoglossal nerve originates in the hypoglossal nucleus of the medulla and supplies motor innervation to all of the muscles of the tongue except the palatoglossus (which is supplied by the vagus). This nerve also contains proprioceptive afferents from the tongue muscles.
Lips and Tongue: Anatomy palsy.
(b): The deviation slightly improved 3 months later.
(c): The deviation disappeared 5 months later for complete recovery of
hypoglossal nerve
Hypoglossal nerve
The 12th cranial nerve. The hypoglossal nerve originates in the hypoglossal nucleus of the medulla and supplies motor innervation to all of the muscles of the tongue except the palatoglossus (which is supplied by the vagus). This nerve also contains proprioceptive afferents from the tongue muscles.
Lips and Tongue: Anatomy function.
LMA: laryngeal mask
airway
Airway
ABCDE Assessment