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Questions and Answers
The goal of imaging in a patient with acute stroke is to identify necrotic brain tissue exclusively.
The goal of imaging in a patient with acute stroke is to identify necrotic brain tissue exclusively.
False
Hypoattenuating brain tissue is a sign of ischemia seen in CT imaging.
Hypoattenuating brain tissue is a sign of ischemia seen in CT imaging.
True
The Dense MCA sign refers to the presence of a clot in the anterior cerebral artery.
The Dense MCA sign refers to the presence of a clot in the anterior cerebral artery.
False
Obscuration of the lentiform nucleus is a common sign of infarction found in middle cerebral artery strokes.
Obscuration of the lentiform nucleus is a common sign of infarction found in middle cerebral artery strokes.
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Ischemic brain tissue is the most resistant region in the brain to suffer from a lack of collateral flow.
Ischemic brain tissue is the most resistant region in the brain to suffer from a lack of collateral flow.
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Hemorrhage is most easily detected through MR-sequences rather than CT imaging.
Hemorrhage is most easily detected through MR-sequences rather than CT imaging.
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15% of middle cerebral artery infarcts are characterized as initially hemorrhagic.
15% of middle cerebral artery infarcts are characterized as initially hemorrhagic.
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ATP is a molecule that stores energy used by all cells in the form of amino acids.
ATP is a molecule that stores energy used by all cells in the form of amino acids.
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Subarachnoid hemorrhage occurs in the space between the dura mater and the skull.
Subarachnoid hemorrhage occurs in the space between the dura mater and the skull.
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Epidural hematomas are commonly associated with fractures of the temporal bone.
Epidural hematomas are commonly associated with fractures of the temporal bone.
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Diffuse axonal injury (DAI) is best visualized on CT scans due to its high sensitivity.
Diffuse axonal injury (DAI) is best visualized on CT scans due to its high sensitivity.
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Intracerebral hemorrhage refers to bleeding inside the skull but outside of the brain tissue.
Intracerebral hemorrhage refers to bleeding inside the skull but outside of the brain tissue.
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The pia mater is the outermost layer of the meninges covering the brain.
The pia mater is the outermost layer of the meninges covering the brain.
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Cerebrospinal fluid is found in the subarachnoid space between the arachnoid mater and the pia mater.
Cerebrospinal fluid is found in the subarachnoid space between the arachnoid mater and the pia mater.
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Complications of traumatic intracranial hemorrhage include increased intracerebral pressure.
Complications of traumatic intracranial hemorrhage include increased intracerebral pressure.
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Subdural hematomas usually result from traumatic tearing of the bridging veins.
Subdural hematomas usually result from traumatic tearing of the bridging veins.
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An epidural hematoma is primarily seen in adults with head injuries.
An epidural hematoma is primarily seen in adults with head injuries.
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A subdural hematoma can cross midline structures.
A subdural hematoma can cross midline structures.
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Acute subdural hematomas often present with hyperdense clotted blood.
Acute subdural hematomas often present with hyperdense clotted blood.
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Chronic subdural hematomas appear hypodense compared to brain parenchyma.
Chronic subdural hematomas appear hypodense compared to brain parenchyma.
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Subdural hematomas are more common in young athletes due to the density of their brain structures.
Subdural hematomas are more common in young athletes due to the density of their brain structures.
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The middle meningeal artery is the structure typically torn during an epidural hematoma.
The middle meningeal artery is the structure typically torn during an epidural hematoma.
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Subacute subdural hematomas are isodense to brain tissue.
Subacute subdural hematomas are isodense to brain tissue.
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As subdural hematomas age, their density increases, making them easier to detect.
As subdural hematomas age, their density increases, making them easier to detect.
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Study Notes
Computed Tomography (CT) Head Scan
- CT scans are used to diagnose head injuries and stroke.
- The scans can identify hemorrhages, tissue damage, and blockages in blood vessels.
Imaging in Acute Stroke
- The goal of imaging in acute stroke is to rule out hemorrhage.
- Differentiate between irreversibly and reversibly impaired brain tissue.
- Identify stenosis or occlusion of intracranial arteries.
- Dead tissue requires intervention to save functional areas.
CT Early Signs of Ischemia
- Hypo-attenuating brain tissue is a sign of ischemia.
- Obscuration of the lentiform nucleus is another sign.
- The insular ribbon sign and dense MCA sign are also indicative.
- Hemorrhagic infarcts occur.
Hypo-attenuating Brain Tissue
- Ischemia causes cytotoxic edema due to ion pump failure, leading to ATP depletion.
- A 1% increase in brain water content corresponds to a 2.5 HU decrease in CT attenuation.
- Infarction occurs due to the location within the MCA territory, causing damage to gray and white matter.
Obscuration of the Lentiform Nucleus
- Blurred basal ganglia (obscuration) indicates infarct.
- It's a common early sign of middle cerebral artery infarction.
- The basal ganglia are commonly involved in MCA infarcts.
Insular Ribbon Sign
- Swelling and hypodensity of the insular cortex show ischemia.
- It's an early CT sign of infarction in the middle cerebral artery territory.
- This region is sensitive to ischemia and is furthest from collateral blood flow.
Dense MCA Sign
- Resulting from a thrombus or embolus in the MCA.
- CT angiography shows occlusion.
- The dense MCA sign is indicative of a blockage within the MCA.
Hemorrhagic Infarcts
- 15% of MCA infarcts start as hemorrhagic.
- Easier to detect with CT.
- Gradient-echo MR may also visually identify the hemorrhages.
Traumatic Intracranial Hemorrhage
- Any bleeding in the brain or skull is a medical emergency.
- Major causes are stroke, trauma, and ruptured aneurysms.
- Increased intracranial pressure results from complications.
Localization of Hemorrhage
- Subarachnoid hemorrhage is bleeding under the arachnoid. Aneurysms are a common cause seen in trauma victims.
- Subdural hematomas are bleedings between the dura mater and arachnoid mater. Bridge veins commonly tear in anticoagulant patients causing bleedings.
- Epidural hematomas involve the space between the dura and skull. Middle meningeal artery ruptures often lead to these.
- Intra-axial hemorrhages are within the brain tissue. Post-trauma contusions often involve the frontal and temporal areas.
- Diffuse axonal injury (DAI) occurs within the gray-white matter junction, typically seen in high-impact injuries.
Anatomy of the Meninges
- Meninges are three membranes enclosing the brain and spinal cord (dura, arachnoid, pia).
- Cerebrospinal fluid (CSF) fills the subarachnoid space between the arachnoid and pia maters.
- Dura mater is the outer meningeal layer, with inner and outer layers.
- Arachnoid mater is a thin layer with delicate fibers linking it to the pia mater.
- Pia mater is the innermost layer covering the brain and spinal cord.
Traumatic Hemorrhage (Epidural Hematoma)
- An epidural hematoma is bleeding between the dura and the skull.
- A common cause is fracture of the temporal bone, and tearing of the middle meningeal artery.
- These bleedings can sometimes span across the midline (ventricles).
Subdural Hematoma
- A subdural hematoma is a collection of blood between the dura and arachnoid.
- It doesn't usually cross the midline, but may occur near dural folds.
- Common in elderly and alcoholics due to atrophy of the brain, with decreased venous support structures that can easily tear.
- Often associated with trauma, vascular issues or anticoagulation.
Subdural Hematoma (Acute)
- This type of subdural hematoma has a midline shift.
- It requires surgical intervention to remove the hematoma.
The Images Show a Subdural Hematoma
- Subdural hematomas can be hyperdense (areas that exhibit increased density) or isodense (are the same density as brain tissue).
- Hyperdense and isodense areas can occur in hyperacute and rebleeding conditions, respectively.
- Displacement of midline structures with obstruction of CSF flow, and dilation of the temporal horn are features of this condition.
- Acute, subacute and chronic subdural hematomas are classified by density, timing and consistency of the blood.
Isodense Subdural Hematoma
- As the hematoma ages, its density decreases, making detection difficult.
- Bilateral subdural hematomas can occur.
- Cases of isodense hematomas may occur in patients with extremely low red blood cell counts, disseminated intravascular coagulation or issues with CSF dilution.
Chronic Subdural Hematoma
- Chronic subdural hematoma (21 days+) is hypo-dense compared to normal brain tissue. This mimics hygroma.
- A hygroma is a CSF leak into the subdural space, as a result of trauma, and associated with torn arachnoid layers.
Subarachnoid Hemorrhage
- Hyperdense blood in the subarachnoid space, especially around the Sylvian fissure, indicative of this condition.
- Often exhibits subgaleal (outside the brain) hemorrhages.
- Commonly associated with brain contusions and contrecoup injuries.
Coupe Contrecoup Type of Injury
- This type of injury has a combination of contusional hemorrhages and subdural hematomas on the affected side of the brain.
- Associated with fractures of either the frontal or temporal lobes.
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Description
Test your knowledge on imaging techniques used in acute stroke cases. This quiz covers key concepts such as ischemia, hemorrhage detection, and specific signs observed in CT and MRI scans. Perfect for medical students and professionals looking to refresh their understanding of cerebral imaging.
