To evaluate the characteristic CT and cerebral angiographic findings in patients with acute spontaneous subdural hematomas and correlate these imaging findings with causes of bleeding and clinical outcome.

Twenty-one patients with nontraumatic acute spontaneous subdural hematoma presenting during the last five years underwent CT scanning and cerebral angiography was performed in twelve. To determine the cause of bleeding, CT and angiographic findings were retrospectively analysed. Clinical history, laboratory and operative findings, and final clinical outcome were reviewed.

The 21 cases of acute spontaneous subdural hematomas were caused by cerebral vascular abnormalities(n=10), infantile hemorrhagic disease(n=5), or were of unknown origin(n=6). All ten cases of cerebral vascular abnormality were confirmed angiographically å six were aneurysms, three were arteriovenous malformations, and one was moyamoya disease. On CT, subarachnoid hemorrhage was seen to be associated with aneurysms, intracerebral hemorrhage with arteriovenous malformations, and intraventricular hemorrhage with moyamoya disease. All five patients with hemorrhagic disease were infants aged 1 — 17 months å characteristic diffuse distribution of subdural hematoma in both temporoparietal-occipital regions is typical.

The average overall mortality rate was 52.4%(ll/2l). In patients with cerebral vascular abnormalities, mortality was as low as 20%(2/l0), but in hemorrhagic disease was high(60%). In cases of unknown origin it was 100%.

Acute spontaneous subdural hematoma is a rare condition, and the mortality rate is high. In patients with acute spontaneous subdural hematoma, as seen on CT, associated subarachnoid or intracerebral hemorrhage is strongly indicative of intracerebral vascular abnormalities such as aneurysm and arteriovenous malformation, and cerebral angiography is necessary. To ensure proper treatment and thus morkedly reduce mortality, the causes of bleeding should be prompty determined by means of cerebral angiography.