Finding-the-Path: Noncontrast CT of the head

Noncontrast CT of the head

Computed tomography without intravenous contrast enhancement indicates a crescentic hyperdense right subdural hematoma extending from the skull base to the high convexity (arrow). The subdural collection extends into the interhemispheric fissure anteriorly (arrow). There is a minimal compression of the body of the right lateral ventricle (arrow). Soft tissue swelling is present over the left parietal region but no fracture is evident (arrow).

Discussion

Subdural hematomas are seen in 10-20% of patients with intracranial trauma and account for 30% of fatal injuries. The most common etiology of subdural hematomas is stretching and tearing of bridging cortical veins in the subdural space due to sudden change in velocity of the head. A definite history of trauma may be absent, especially in elderly patients. Subdural hematomas occur between the dura and arachnoid. The characteristic CT appearance of an acute subdural hematoma is a crescentic, hyperdense extraaxial collection that spreads diffusely over the affected hemisphere. Subdural hematomas commonly occur over the frontoparietal convexities and in the middle cranial fossa. Subdural hematomas undergo clot lysis and organization over time. Within a few days to a few weeks after trauma, subacute subdural hematomas become nearly isodense with the underlying brain parenchyma. Chronic subdural hematomas are typically low attenuation. In 5% of cases, recurrent hemorrhage into a preexisting chronic subdural hematoma produces a mixed density collection. Mortality rates from a traumatic acute subdural hematoma is very high, ranging from 50 to 85%.

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