On exam, he was disoriented to place and time but had no focal neurologic deficit. His laboratory values were unremarkable. Plain films of the cervical spine showed degenerative spondylosis but no fracture. 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.