Symptomatic subacute subdural haematoma following spontaneous acute subdural haematoma.

Two patients with non-traumatic acute subdural haematoma were observed, initially without surgical intervention. Eleven days after the onset, each patient developed hemiparesis and an increase in severity of headache. Serial computed tomography scans demonstrated that the initial hyperdense haematomas became hypodense with a definite increase in volume. The term "symptomatic subacute subdural haematoma" was proposed to properly define this pathological process, which necessitated removal of the haematoma in the subacute stage. The mechanism of increase in the volume of the haematoma is discussed.