Imaging of the Head and Brain

CT

Overview

• Images of the head are obtained from a rotating beam of X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests particles.
• The images can be adjusted to highlight different structures:
  • Soft tissue Soft Tissue Soft Tissue Abscess windows
  • Bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types windows
• CT with contrast:
  • IV administration of iodinated contrast agent
  • Enhances vascular structures and areas of discontinuity of the blood– 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 barrier
  • Also highlights pathology that interrupts the blood– 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 barrier (i.e., infection, neoplasm, infarction)
  • MRI contraindicated or unavailable

Structures and planes

• The final image depends on the attenuation of the beam by the cranial structures:
  • Bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types: appears white (↑ density, greater attenuation)
  • Air: appears black (↓ density, lower attenuation)
  • White matter White Matter The region of central nervous system that appears lighter in color than the other type, gray matter. It mainly consists of myelinated nerve fibers and contains few neuronal cell bodies or dendrites. Brown-Séquard Syndrome appears slightly darker than gray matter Gray matter Region of central nervous system that appears darker in color than the other type, white matter. It is composed of neuronal cell bodies; neuropil; glial cells and capillaries but few myelinated nerve fibers. Cerebral Cortex: Anatomy because of the presence of fat in myelin (which has lower density than water).
• 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 pathology exhibits different attenuation, such as:
  • Hemorrhage: high attenuation (appears bright)
  • Infarct Infarct Area of necrotic cells in an organ, arising mainly from hypoxia and ischemia Ischemic Cell Damage: low attenuation (appears dark owing to 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)
• Complete study of the head includes the following planes:
  • Axial Axial Computed Tomography (CT) 
  • Coronal Coronal Computed Tomography (CT)
  • Sagittal Sagittal Computed Tomography (CT)

MRI

Overview

• Technique that uses magnetic fields and radiofrequency pulses to produce highly detailed images of the human 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.
• Operates on the principle that the body is abundant in protons, which align with a strong magnetic field:
  • Protons spin out of 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 when a radiofrequency current is applied.
  • When current is removed, the protons realign, but differences depend on the nature 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 structure.
• Images are processed on the basis of the intrinsic tissue relaxation:
  • T1: relaxation time for the protons to align longitudinal/parallel to the magnetic field
  • T2: relaxation time for the protons to align transverse/perpendicular to the magnetic field 
• MRI with contrast:
  • Use of gadolinium-based agent
  • Increases detectability of lesion(s)
• Additional sequences can include:
  • Fluid-attenuated inversion recovery Fluid-Attenuated Inversion Recovery Magnetic Resonance Imaging (MRI) ( FLAIR FLAIR Magnetic Resonance Imaging (MRI)):
    • Fluid-sensitive sequence that nullifies signal from water.
    • This nullification allows other T2 signals to be more prominent ( 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).
  • Diffusion-weighted imaging (DWI) and apparent diffusion Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially facilitated diffusion, is a major mechanism of biological transport. Peritoneal Dialysis and Hemodialysis coefficient (ADC):
    • Sequence that detects Brownian motion of atoms
    • Useful for detecting ischemic areas from stroke and for differentiating 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 tumors
  • Gradient echo (GRE) or susceptibility-weighted imaging (SWI):
    • T2-sensitive sequence that manipulates ferromagnetic signal
    • This manipulation produces a larger area of signal loss around calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes and blood.

Structures and planes

• Appearance of the images depend on the intrinsic tissue relaxation.
• Descriptions (generally by shades of gray):
  • Hyperintense Hyperintense Magnetic Resonance Imaging (MRI): bright (white)
  • Isointense: same brightness as the tissue it is being compared to
  • Hypointense Hypointense Magnetic Resonance Imaging (MRI): darker than the tissue it is being compared to
• Similar to CT, the planes are:
  • Axial Axial Computed Tomography (CT) 
  • Coronal Coronal Computed Tomography (CT)
  • Sagittal Sagittal Computed Tomography (CT)

MRI and 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 tissue

Other Imaging

Ultrasonography

• The main principle of ultrasonographic imaging is the transmission and reflection of sound waves through the tissues.
• Readily available, with images obtained in real time
• Less expensive and noninvasive
• No ionizing radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma
• Requires an adequate acoustic window (not obstructed by bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types or impeded by air); thus, it has limited use in neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant, but it is used in:
  • Fetal and neonatal screening Screening Preoperative Care
  • Examination of infant requiring ECMO to detect intracranial hemorrhage Intracranial hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most sahs originate from a saccular aneurysm in the circle of willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage
  • Doppler Doppler Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. Ultrasound (Sonography) evaluation of the carotid artery

Nuclear medicine Nuclear medicine A specialty field of radiology concerned with diagnostic, therapeutic, and investigative use of radioactive compounds. Nuclear Imaging

• SPECT SPECT An imaging technique using a device which combines tomography, emission-computed, single-photon and tomography, x-ray computed in the same session. Nuclear Imaging and PET PET An imaging technique that combines a positron-emission tomography (PET) scanner and a ct X ray scanner. This establishes a precise anatomic localization in the same session. Nuclear Imaging scans:
  • Functional assessment 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
  • SPECT SPECT An imaging technique using a device which combines tomography, emission-computed, single-photon and tomography, x-ray computed in the same session. Nuclear Imaging has wider availability and is less expensive.
  • PET PET An imaging technique that combines a positron-emission tomography (PET) scanner and a ct X ray scanner. This establishes a precise anatomic localization in the same session. Nuclear Imaging has superior image quality Quality Activities and programs intended to assure or improve the quality of care in either a defined medical setting or a program. The concept includes the assessment or evaluation of the quality of care; identification of problems or shortcomings in the delivery of care; designing activities to overcome these deficiencies; and follow-up monitoring to ensure effectiveness of corrective steps. Quality Measurement and Improvement (contrast and resolution) but is more expensive.
• Used with CNS tumors, seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures/ 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, and 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

Intracranial Masses and Anomalies

Cerebral 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

• Processes related to shifts in water in 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 parenchyma in response to different forms 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 injury
• Types:
  • Vasogenic:
    • Extracellular 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 due to compromised blood– 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 barrier (↑ permeability) 
    • 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 seen primarily in the white matter White Matter The region of central nervous system that appears lighter in color than the other type, gray matter. It mainly consists of myelinated nerve fibers and contains few neuronal cell bodies or dendrites. Brown-Séquard Syndrome
    • Seen in mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast/neoplasm or hemorrhage 
    • CT: gray-white matter differentiation with 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 localized to the white matter White Matter The region of central nervous system that appears lighter in color than the other type, gray matter. It mainly consists of myelinated nerve fibers and contains few neuronal cell bodies or dendrites. Brown-Séquard Syndrome
    • MRI: hyperintense Hyperintense Magnetic Resonance Imaging (MRI) T2
  • Cytotoxic Cytotoxic Parvovirus B19:
    • Water passes into the cell → hydropic cellular swelling Cellular Swelling Cell Injury and Death
    • 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 primarily in the gray matter Gray matter Region of central nervous system that appears darker in color than the other type, white matter. It is composed of neuronal cell bodies; neuropil; glial cells and capillaries but few myelinated nerve fibers. Cerebral Cortex: Anatomy and without expansion of extracellular space
    • Caused by infarction/ 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
    • Seen well in MRI with DWI
  • Combined:
    • 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: initially cytotoxic Cytotoxic Parvovirus B19, then vasogenic changes occur hours later
    • Also in cases of trauma, infection, encephalopathy Encephalopathy Hyper-IgM Syndrome
  • Interstitial:
    • Due to transependymal flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure of CSF
    • Hydrocephalic

Hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage

• Increase in volume of CSF resulting in the expansion of the ventricular system Ventricular System The ventricular system is an extension of the subarachnoid space into the brain consisting of a series of interconnecting spaces and channels. Four chambers are filled with cerebrospinal fluid (CSF): the paired lateral ventricles, the unpaired 3rd ventricle, and the unpaired 4th ventricle. Ventricular System: Anatomy
• May be due to the overproduction, decreased absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption, or obstruction of CSF flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure 
• Classified as communicating (nonobstructive) and noncommunicating (obstructive)
• Imaging:
  • MRI (preferred imaging):
    • Detects malformations and tumors that could cause hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage
    • Provides information regarding CSF flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure dynamics
  • Ultrasonography:
    • Used in newborns and young infants
    • Cannot be used when anterior fontanelles Fontanelles Physical Examination of the Newborn close
  • Finding: markedly dilated ventricles compared to the sulci

Congenital Congenital Chorioretinitis anomalies

• MRI is superior in detecting intracranial abnormalities (better details and tissue contrast).
• CT is used when evaluation of osseous structures is needed.

Tumors

• Types:
  • Intracranial or intraaxial: within the cerebral parenchyma (e.g., gliomas, intracranial metastasis Metastasis The transfer of a neoplasm from one organ or part of the body to another remote from the primary site. Grading, Staging, and Metastasis)
  • Extraaxial: outside the cerebral parenchyma, but within the 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 (e.g., 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)
• MRI with contrast: provides optimal evaluation 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 tumors
• CT:
  • Lower resolution of soft tissues
  • Used in the following:
    • Emergency setting
    • View involvement of bony structures (i.e., bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types destruction of tumors)
    • MRI contraindicated
• Examples:
  • 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:
    • Lesion with dural tail (marginal dural thickening tapering peripherally) 
    • MRI: hypointense Hypointense Magnetic Resonance Imaging (MRI) on T1- or hyperintense Hyperintense Magnetic Resonance Imaging (MRI) on T2-weighted images
    • CT: well-defined extraaxial mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast, which can contain calcifications
  • Glioblastoma multiforme Glioblastoma multiforme Glioblastoma multiforme is a high-grade astrocytoma, an aggressive brain tumor arising from astrocytes, with an unknown cause and a poorly understood link to risk factors. There are two main types: primary, a more aggressive form seen more commonly in older patients, and secondary, developing from lower-grade astrocytomas and seen more commonly in younger patients. Glioblastoma Multiforme:
    • Malignant 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 tumors that rapidly progress and have poor prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas
    • MRI (best study): heterogeneously isointense or hypointense Hypointense Magnetic Resonance Imaging (MRI) on T1, heterogeneously hyperintense Hyperintense Magnetic Resonance Imaging (MRI) on T2 and with rim enhancement 
  • 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 metastasis Metastasis The transfer of a neoplasm from one organ or part of the body to another remote from the primary site. Grading, Staging, and Metastasis:
    • Invasion of cerebral tissue after systemic dissemination of malignancy Malignancy Hemothorax (prostatic, uterine, GI, and breast tumors)
    • Contrast-enhanced MRI: most sensitive method

Ischemia and Hemorrhage

Stroke (ischemic)

Stroke is a medical emergency caused by interruption or reduction of blood supply to 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. Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant is obtained on all patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship in whom stroke is suspected to determine etiology, magnitude of damage, and management. 

Types of stroke:

• Ischemic: can be thrombotic (e.g., atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis) or embolic (e.g., atrial fibrillation Atrial fibrillation Atrial fibrillation (AF or Afib) is a supraventricular tachyarrhythmia and the most common kind of arrhythmia. It is caused by rapid, uncontrolled atrial contractions and uncoordinated ventricular responses. Atrial Fibrillation)
• Hemorrhagic

Acute stroke evaluation:

• Non-contrast-enhanced CT (NCCT) is the initial test:
  • Advantages:
    • Sensitivity in detecting hemorrhage (thus affects management)
    • Rapid scan time
    • Widespread availability
  • NCCT findings of 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:
    • Normal in hyperacute phase
    • Hyperdense vessel sign (“bright artery sign”) on NCCT indicates thrombus in the artery.
    • Loss of gray/white differentiation
    • Parenchymal hypodensity
    • Sulcal effacement
    • > 24 hours: better-defined hypodense area
• CTA CTA A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests:
  • Used for patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship who are candidates for endovascular therapy in the setting of emergent large-vessel occlusion.
• MRI:
  • MRI with DWI: most sensitive test, detecting changes within 20–30 minutes of onset
  • Limited availability
  • Generally longer scan times
  • Difficulty of transporting and monitoring unstable patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
  • Certain contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation (e.g., pacemakers)

Hemorrhage

• Multiple etiologies:
  • Hypertensive vasculopathy Hypertensive Vasculopathy Intracerebral Hemorrhage: most common cause of spontaneous intracerebral hemorrhage Intracerebral Hemorrhage Intracerebral hemorrhage (ICH) refers to a spontaneous or traumatic bleed into the brain parenchyma and is the 2nd-most common cause of cerebrovascular accidents (CVAs), commonly known as stroke, after ischemic CVAs. Intracerebral Hemorrhage
  • Other: trauma, arteriovenous malformation Arteriovenous malformation Abnormal formation of blood vessels that shunt arterial blood directly into veins without passing through the capillaries. They usually are crooked, dilated, and with thick vessel walls. A common type is the congenital arteriovenous fistula. The lack of blood flow and oxygen in the capillaries can lead to tissue damage in the affected areas. Erysipelas, drugs, tumors, bleeding disorders Bleeding disorders Hypocoagulable conditions, also known as bleeding disorders or bleeding diathesis, are a diverse group of diseases that result in abnormal hemostasis. Physiologic hemostasis is dependent on the integrity of endothelial cells, subendothelial matrix, platelets, and coagulation factors. The hypocoagulable states result from abnormalities in one or more of these contributors, resulting in ineffective thrombosis and bleeding. Hypocoagulable Conditions, antithrombotic therapy
  • Type of bleeding and hemorrhage partly dependent on etiology
• Imaging:
  • NCCT (initial test of choice):
    • Hemorrhage = hyperdense area 
    • Mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast effect may be apparent (midline shift, herniation Herniation Omphalocele, hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage).
  • MRI:
    • More sensitive
    • Used as adjunct if clinical suspicion for hemorrhage is high and CT is negative
    • In hyperacute phase, hemorrhage is hyperintense Hyperintense Magnetic Resonance Imaging (MRI) (T2-weighted).
• Different findings ( intracranial hemorrhage Intracranial hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most sahs originate from a saccular aneurysm in the circle of willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage):
  • Intracerebral (within the cerebral parenchyma):
    • Usually caused by 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, 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 rupture, amyloid deposition, and trauma
    • Can be accompanied by intraventricular hemorrhage Intraventricular hemorrhage Bleeding within the cerebral ventricles. It is associated with intraventricular trauma, aneurysm, vascular malformations, hypertension and in very low birth weight infants. Intracerebral Hemorrhage (hyperdensity within cerebral ventricles)
  • Epidural (between the dura and the 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):
    • Usually caused by 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 (tearing of the medial meningeal artery)
    • High density
    • Lens-shaped/biconvex pattern
    • Does not cross suture lines but can cross midline
  • Subdural (between the dura mater Dura mater The outermost of the three meninges, a fibrous membrane of connective tissue that covers the brain and the spinal cord. Meninges: Anatomy and arachnoid membranes):
    • Usually caused by trauma (damage to the bridging veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology)
    • High density
    • Crescent-shaped
    • Crosses suture lines but does not cross midline
  • Subarachnoid (in the subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage):
    • Usually caused by an 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 rupture or trauma
    • Hyperdensity confined to the subarachnoid space Subarachnoid space The space between the arachnoid membrane and pia mater, filled with cerebrospinal fluid. It contains large blood vessels that supply the brain and spinal cord. Subarachnoid Hemorrhage, the sulci, fissures, and the basal cisterns

Brain Injury and Herniation

Traumatic 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 injury (TBI)

• Definition: 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 pathology or altered 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 function stemming from an external force
• Injury mechanisms:
  • Coup: injury at the point of impact
  • Contrecoup: injury at the point opposite to the site of impact
• 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 results in:
  • Hemorrhage due to shearing forces Shearing forces Vascular Resistance, Flow, and Mean Arterial Pressure applied to blood vessels until rupture
  • Diffuse axonal injury Diffuse axonal injury A relatively common sequela of blunt head injury, characterized by a global disruption of axons throughout the brain. Associated clinical features may include neurobehavioral manifestations; persistent vegetative state; dementia; and other disorders. Head Trauma due to stretching forces applied to the axons Axons Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body. Nervous System: Histology 
• Imaging:
  • NCCT: done in the acute setting to identify need for neurosurgical intervention (e.g., hemorrhage) and emergent medical management
  • MRI:
    • More sensitive in detecting diffuse axonal injury Diffuse axonal injury A relatively common sequela of blunt head injury, characterized by a global disruption of axons throughout the brain. Associated clinical features may include neurobehavioral manifestations; persistent vegetative state; dementia; and other disorders. Head Trauma and other parenchymal lesions
    • Obtained in persistent or progressive neurologic deficit with negative CT
    • For subacute evaluation of TBI

Herniation Herniation Omphalocele

• Definition: A portion 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 is displaced from one compartment to another due to mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast effect, causing a potentially life-threatening condition. 
• Imaging:
  • NCCT:
    • Initial test of choice in the emergency setting
    • Readily available and can be obtained quickly
  • MRI: provides improved tissue characterization
• Findings:
  • Subfalcine: displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms of the cingulate gyrus Cingulate gyrus One of the convolutions on the medial surface of the cerebral hemispheres. It surrounds the rostral part of the brain and corpus callosum and forms part of the limbic system. Limbic System: Anatomy under the falx cerebri 
  • Transtentorial:
    • Downward displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms 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 from the supratentorial compartment (e.g., central herniation Herniation Omphalocele, uncal herniation Uncal Herniation Increased Intracranial Pressure (ICP))
    • Upward displacement Displacement The process by which an emotional or behavioral response that is appropriate for one situation appears in another situation for which it is inappropriate. Defense Mechanisms 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 from the posterior fossa (e.g., cerebellar hemispheres)
  • Tonsillar: 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 displaced caudally and through the foramen magnum
  • External: herniation Herniation Omphalocele 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 through a 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 defect (e.g., traumatic or postsurgical)