Intracranial hemorrhage CT

CAT scan (computed axial tomography) is the definitive tool for accurate diagnosis of an intracranial hemorrhage.

Cerebral Amyloid Angiopathy

• Cerebral amyloid angiopathy manifests radiologically as part or all of a constellation of findings including:
  • Acute or chronic ICHs in a distinctive cortical-subcortical distribution
  • Leukoencephalopathy
  • Atrophy

• CT allows rapid establishment of the presence or absence of an ICH and exclusion of an acute cerebral infarction.
• Non-enhanced head CT is the preferred imaging modality for initial work-up as it provides crucial information regarding the characteristics of the ICH, including size, location, shape, and extension to the extraaxial spaces
• If an ICH is present in a cortical-subcortical location suspicious for Cerebral amyloid angiopathy, the patient should undergo additional evaluation with MR imaging.
• GRE is currently the most sensitive MR imaging sequence for detection of the chronic cortical-subcortical microhemorrhage.

Epidural Hematoma

• Typical appearance is a biconvex, elliptical, extra-axial fluid collections.
• Acute EDH may contain both a hyperattenuating clot and a swirling lucency (believed to represent a mixture of active bleeding and the serum remaining after previous clot formation).
• Subacute EDH becomes homogeneously hyperattenuating.
• Chronic EDH is at least partly hypoattenuating as the clot undergoes breakdown and resorption.

Images courtesy of RadsWiki

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  CT: Epidural hematoma

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  CT: Epidural hematoma

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  CT: Epidural hematoma

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  CT: Epidural hematoma

Intracerebral Parenchymal Hemorrhage

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  CT: Intracerebral parenchymal hemorrhage

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  CT: Intracerebral parenchymal hemorrhage

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  CT: Intracerebral parenchymal hemorrhage

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  CT: Intracerebral parenchymal hemorrhage

Intraventricular Hemorrhage

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  CT: Intraventricular hemorrhage

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  CT: Intraventricular hemorrhage

Subarachnoid Hemorrhage

Computed Tomography

• Subarachnoid hemorrhage appears as a high-attenuating, amorphous substance that fills the normally dark CSF-filled subarachnoid spaces.
• These findings are most evident in the largest subarachnoid spaces, such as the suprasellar cistern and Sylvian fissures.
• Acute Subarachnoid hemorrhage is typically 50-60 HU.
• When CT scanning is performed several days to weeks after the initial bleed, the findings are more subtle.
  • The initial high-attenuation of blood and clot tend to decrease, and these appear as intermediate gray.
  • These findings can be isointense relative to normal brain parenchyma.
• In addition to detecting Subarachnoid hemorrhage, CT is useful in localizing the source of bleeding.

Images courtesy of RadsWiki

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  CT: Diffuse subarachnoid hemorrhage

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  CT: Diffuse subarachnoid hemorrhage

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  CT: Diffuse subarachnoid hemorrhage

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  CT: Diffuse subarachnoid hemorrhage

MRI

• Fluid-attenuated inversion recovery (FLAIR) is the most sensitive MRI pulse sequence for the detection of SAH. SAH appears as high-intensity signal in normally low signal CSF spaces.
• T2- and T2*-weighted images can potentially demonstrate SAH as low signal intensity in normally high-signal subarachnoid spaces.
• On T1-weighted images, acute SAH may appear as intermediate- or high-intensity signal in the subarachnoid space.
• MR angiography may be useful in the evaluation of aneurysms and other vascular lesions that cause SAH.

Subdural Hemorrhage

Computed Tomography

• Unlike epidural hematomas, subdural hematomas are not restricted by dural tethering at the cranial sutures.
  • They can cross suture lines and continue along the falx and tentorium.
  • They do not cross the midline because of the meningeal reflections.

• In the acute phase, subdural hematomas appear as a crescent-shaped extra-axial collection with increased attenuation that, when large enough, causes effacement of the adjacent sulci and midline shift.
• The attenuation changes as the hematoma ages.

• Subacute subdural hematomas may be difficult to detect because they may have isoattenuation compared with adjacent gray matter

• Chronic subdural hematomas have isoattenuation relative to the cerebrospinal fluid.

• Rebleeding into subdural hematomas also may occur and is depicted as a layer of high-attenuation hemorrhage within a lower attenuation hematoma.

Images courtesy of RadsWiki

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  CT: Subdural hemorrhage

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  CT: Subdural hemorrhage

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  CT: Subdural hemorrhage

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  CT: Subdural hemorrhage

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  CT: Subdural hemorrhage

MRI

• MRI is more sensitive than CT scanning in the detection of subdural hematomas because the multiplanar and superior tissue differentiation of MRI makes detection easier.

• The shape of the subdural hematoma on axial images is the same crescent-shaped pattern seen on CT scan images.

• The signal depends on the age of the hemorrhage and follows the signal pattern of intraparenchymal hematomas in acute and subacute cases.
• Chronic subdural hematomas, which appear as isoattenuation relative to CSF on CT scans, often demonstrate increased signal intensity on T1-weighted images because of the presence of free methemoglobin, though the intensity decreases over time.

Perimesencephalic Hemorrhage

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  CT: Perimesencephalic hemorrhage

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  CT: Perimesencephalic hemorrhage

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  CT: Perimesencephalic hemorrhage