Computed Tomography in Acute Stroke Imaging

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Questions and Answers

What is the primary goal of imaging in a patient with acute stroke?

  • Assess the level of consciousness
  • Evaluate the duration of symptoms
  • Differentiate between hemorrhage and ischemia (correct)
  • Identify the exact location of the brain tumor

Which of the following is an early CT sign of ischemia?

  • Obscuration of the lentiform nucleus (correct)
  • Bilateral cortical atrophy
  • Increased density of brain tissue
  • Thickening of the cranial bones

What does the Insular Ribbon sign indicate on a CT scan?

  • Presence of a brain tumor
  • Early infarction in the MCA territory (correct)
  • Cortical necrosis
  • Hemorrhagic transformation

Why do we observe ischemia on a CT scan?

<p>Because of cytotoxic edema from ion-pump failure (D)</p> Signup and view all the answers

What does the Dense MCA sign suggest in a CT angiography?

<p>Occlusion of the middle cerebral artery (A)</p> Signup and view all the answers

What percentage of MCA infarcts are initially hemorrhagic?

<p>15% (C)</p> Signup and view all the answers

What correlates with the decrease in CT attenuation when brain water content increases?

<p>Decrease of 2.5 HU for each percent (B)</p> Signup and view all the answers

What can be seen as a result of inadequate ATP supply in the brain?

<p>Cytotoxic edema development (B)</p> Signup and view all the answers

What is the most common cause of traumatic intracranial hemorrhage?

<p>Trauma (D)</p> Signup and view all the answers

Which type of intracranial hemorrhage occurs most commonly from rupture of an aneurysm?

<p>Subarachnoid hemorrhage (A)</p> Signup and view all the answers

What is a primary complication of traumatic intracranial hemorrhage?

<p>Hydrocephalus from CSF obstruction (A)</p> Signup and view all the answers

What anatomical structure separates the dura mater from the skull?

<p>Epidural space (B)</p> Signup and view all the answers

Which layer of the meninges allows blood vessels to nourish the brain?

<p>Pia mater (D)</p> Signup and view all the answers

In patients on anticoagulant therapy, which type of hematoma is most likely to occur?

<p>Subdural hematoma (B)</p> Signup and view all the answers

What type of injury is characterized by diffuse axonal injury (DAI)?

<p>High velocity injuries (A)</p> Signup and view all the answers

Which of the following describes an epidural hematoma?

<p>Bleeding between the dura mater and the skull (A)</p> Signup and view all the answers

What is the primary cause of an epidural hematoma?

<p>Tearing of the middle meningeal artery (C)</p> Signup and view all the answers

How does a subdural hematoma typically present in terms of location?

<p>It is located within the inner layer of the dura and the arachnoid. (D)</p> Signup and view all the answers

Which population is most commonly associated with subdural hematomas?

<p>Patients taking anticoagulants (D)</p> Signup and view all the answers

What differentiates an acute subdural hematoma's appearance from a chronic one?

<p>Acute appears hyperdense, while chronic appears hypodense. (C)</p> Signup and view all the answers

In which scenario is a subdural hematoma most likely to be detected as isodense?

<p>As it ages and its density decreases (C)</p> Signup and view all the answers

What characteristic is common to both hyperacute and rebleeding subdural hematomas?

<p>They show both hyperdense and isodense areas. (C)</p> Signup and view all the answers

Why is an epidural hematoma more likely to cross the midline than a subdural hematoma?

<p>Due to its location between the dura and the skull. (A)</p> Signup and view all the answers

What is a typical sign of active bleeding in an acute subdural hematoma?

<p>Mixed components of fresh and clotted blood (C)</p> Signup and view all the answers

Flashcards

What is the goal of imaging in acute stroke?

The goal of imaging in a patient with acute stroke is to identify the cause of the stroke, determine the extent of brain damage, and assess the risk of further damage. This allows for appropriate medical management.

What does hypodense brain tissue on a CT scan suggest?

Hypodense brain tissue on a CT scan can indicate ischemia, which is a lack of blood flow to the brain. It typically occurs in the territory of the middle cerebral artery (MCA) and involves both gray and white matter.

What is the significance of an obscured lentiform nucleus on a CT scan?

The lentiform nucleus is a part of the basal ganglia, a critical area for movement control. Obscuration, or blurring of the lentiform nucleus, is a major sign of stroke in the middle cerebral artery territory, as this area is almost always affected.

What is the insular ribbon sign and why is it important in stroke imaging?

The insular cortex, a brain region deep in the folds, swells and becomes hypodense in strokes affecting the middle cerebral artery. This location is particularly vulnerable to ischemic damage due to its distance from collateral blood supply.

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What is the 'dense MCA sign' and what does it tell us?

A dense MCA sign on CT indicates a blockage in the middle cerebral artery from a thrombus (blood clot) or embolus (traveling clot). This blockage prevents blood flow to the brain, causing ischemic damage.

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What are hemorrhagic infarcts and how are they viewed?

Hemorrhagic infarcts occur when a stroke causes bleeding into the brain tissue in addition to ischemic damage. They can be identified on CT and are associated with a higher risk of complications.

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What is the significance of the middle cerebral artery (MCA) in stroke imaging?

The middle cerebral artery (MCA) is a major blood vessel supplying blood to a large part of the brain. It is vulnerable to blockages that can lead to stroke, as seen in the dense MCA sign.

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What is ATP and what role does it play in stroke?

ATP stands for adenosine triphosphate, which is the primary energy source for cells. In stroke, ATP production plummets due to the lack of oxygen, disrupting normal cell function and leading to brain damage.

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Traumatic Intracranial Hemorrhage

Bleeding inside the skull or brain, a medical emergency.

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Subarachnoid Hemorrhage

Rupture of an aneurysm or trauma, causing bleeding under the arachnoid membrane.

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Subdural Hematoma

Bleeding between the dura mater and arachnoid, often from traumatic tearing of bridging veins.

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Epidural Hematoma

Bleeding in the space between the dura mater and the skull, often from a temporal bone fracture.

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Intracerebral Hemorrhage

Bleeding within the brain tissue itself, often from a small post-traumatic hemorrhage.

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Diffuse Axonal Injury (DAI)

Diffuse injury at the gray-white matter junction, seen in high-velocity injuries.

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Dura Mater

The outermost layer of the meninges that covers the brain and spinal cord.

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Pia Mater

The innermost layer of the meninges that covers the brain.

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Subdural Hematoma Spread

A subdural hematoma can spread along the dural folds like the falx (dividing the cerebrum) and tentorium (separating the cerebrum from the cerebellum).

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Heterogeneous Subdural Hematoma

A subdural hematoma can appear mixed in density due to fresh (hypodense) and clotted (hyperdense) blood, making it appear heterogenous.

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Isodense Subdural Hematoma

As a subdural hematoma ages, it becomes less dense and may match the density of the brain, making it difficult to detect.

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Midline Shift in Subdural Hematoma

A subdural hematoma can cause midline shift, compressing brain tissue and obstructing CSF flow, leading to ventricular dilation, particularly in the temporal horn.

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Density of Subdural Hematomas Over Time

An acute subdural hematoma appears hyperdense (bright), a subacute one is isodense (similar to brain), and a chronic one is hypodens (darker).

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Density Variability in Subdural Hematoma

The density of a subdural hematoma can vary depending on its age and the presence of fresh bleeding, making it appear hyperdense, isodense, or hypodense.

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Study Notes

Computed Tomography (CT) Head Scan

  • Prepared by Ahmed Jasem Abass, MSC Medical

Imaging in Acute Stroke

  • Goal of imaging in acute stroke is to exclude hemorrhage
  • Differentiate between irreversibly affected brain tissue and reversibly impaired tissue
  • Identify stenosis or occlusion of major intracranial arteries

CT Early Signs of Ischemia

  • Hypo-attenuating brain tissue
  • Obscuration of the lentiform nucleus
  • Insular Ribbon sign
  • Dense MCA sign
  • Hemorrhagic infarcts

Hypo Attenuating Brain Tissue

  • Ischemia causes cytotoxic edema due to ion pump failure, requiring ATP
  • 1% increase in brain water content results in a 2.5 HU decrease in CT attenuation
  • Diagnosis of infarction is based on MCA location and involvement of gray and white matter

Obscuration of the Lentiform Nucleus

  • Blurred basal ganglia, an important sign of infarction
  • Seen in middle cerebral artery (MCA) infarction
  • One of the earliest and most frequent signs

Insular Ribbon Sign

  • Refers to hypodensity and swelling of the insular cortex
  • A subtle early CT sign of infarction in the middle cerebral artery territory
  • Sensitive to ischemia due to being furthest from collateral flow
  • Differentiate from herpes encephalitis

Dense MCA Sign

  • Result of thrombus or embolus in the MCA
  • Visible on CT angiography as MCA occlusion

Hemorrhagic Infarcts

  • 15% of MCA infarcts are initially hemorrhagic
  • Hemorrhage easily detected with CT, also visualized with gradient echo MR sequences

Traumatic Intracranial Hemorrhage

  • Any bleeding inside the skull or brain is a medical emergency
  • Common causes include stroke, trauma, and ruptured aneurysms
  • Complications include increased intracerebral pressure, edema, and hydrocephalus

Localization of Hemorrhage

  • Subarachnoid Hemorrhage: Acute bleeding under the arachnoid membrane, often due to aneurysm rupture
  • Subdural Hematoma: Bleeding between the dura and arachnoid membranes, usually from bridging vein rupture, common in elderly and patients on anticoagulants
  • Epidural Hematoma: Bleeding between the dura and skull, often due to temporal bone fracture and middle meningeal artery rupture
  • Intra-axial Hemorrhage (Intracerebral): Cerebral hemorrhagic contusion, post-traumatic small hemorrhages located near the skull, often frontobasal and anterior in temporal lobes
  • Diffuse Axonal Injury (DAI): Diffuse injury at the gray-white matter junction, seen in high-velocity injuries and low sensitivity for CT, better seen on MRI.

Anatomy of the Meninges

  • Meninges are three membranes (dura, arachnoid, and pia) enveloping brain and spinal cord
  • Cerebrospinal fluid (CSF) is found in the subarachnoid space between arachnoid and pia
  • Dura mater is the outermost meningeal layer, with two layers (inner and outer)
  • Arachnoid mater is the delicate layer with fibers extending to pia
  • Pia mater is the innermost layer, allowing nutrient blood vessels to pass through the brain

Traumatic Hemorrhage (Epidural Hematoma)

  • Bleeding between dura and skull
  • Common in children with head injury and temporal bone fractures, leading to tearing of the middle meningeal artery
  • Usually does not cross suture lines.

Subdural Hematoma

  • Collection of blood between inner dura and arachnoid membranes
  • Cannot cross the midline
  • Usually due to cortical bridging vein rupture, especially in elderly and alcoholics with atrophy
  • Venous structures are less packed, increasing space for rupture.

Subdural Hematoma (CT Findings)

  • Acute: High-density, hyperdense
  • Chronic: Low-density, hypodensity.
  • Midline shift seen on CT (left image example given)

The Images Show a Subdural Hematoma

  • Hematoma displays both hyperdense and isodense areas (indicative of both acute and chronic bleeding).
  • Displacement of midline structures and CSF flow obstruction (dilated temporal horn of the right lateral ventricle).
  • Acute: Hyperdense (clotted blood); Subacute: Isodense; Chronic: Hypodense (relative to brain parenchyma)
  • Heterogeneous appearance in acute setting due to combination of both fresh and clotted blood.

Isodense Subdural Hematoma

  • Aging hematomas decrease in density, matching that of the brain, making them harder to detect on CT.
  • Can be bilateral.
  • Rare case appearance: isodense to brain tissue; e.g., in patients with severe anemia, disseminated intravascular coagulation, or dilution with CSF.

Chronic Subdural Hematoma

  • Appears hypodensity to parenchyma and isodensity to CSF after 21 days
  • Can mimic a hygroma
  • Hygroma is due to traumatic tear in the arachnoid layer that causes CSF leak into the subdural space

Subarachnoid Hemorrhage

  • Hyperdense blood in the subarachnoid space (Sylvian fissure).
  • Can have subgaleal hemorrhage in the occipital region.
  • Often due to coupe contrecoup type injuries (double impact trauma)

Coupe Contrecoup Type of Injury

  • Characterized by contusional hemorrhages, subdural hematoma, and subarachnoid hemorrhage on opposite side of the impact site.
  • Often associated with parietal bone fracture and subarachnoid hemorrhage.

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