subdural hematoma

subdural hematoma n a hematoma that occurs between the dura mater and arachnoid in the subdural space and that may apply neurologically significant pressure to the cerebral cortex

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accumulation of blood between the dura mater and the arachnoid, resulting in the creation of an abnormal space (subdural space, q.v.). In the severe acute form, both blood and cerebrospinal fluid enter the space as a result of laceration of the brain and a tear in the arachnoid, adding subdural compression to the direct injury to the brain. In the chronic form, only blood effuses into the subdural space as a result of rupture of the bridging veins, usually due to closed head injury. The effusion is a gradual process resulting, weeks after the injury, in headache and progressive focal signs that reflect the location of the mass.

Acute focal subdural hematoma of the left frontal area of a six-month-old infant. The layering of subdural blood is due to rapid collection and consists of newly clotted blood and fresh hemorrhage.