Acute Stroke Imaging Quiz

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.