Abstract
We present a case of nontraumatic acute subdural hematoma (SDH) caused by rupture of a middle cerebral artery (MCA) aneurysm. A 74-year-old man presented after sudden onset of moderate headache. Neurological examination on arrival revealed no abnormalities, but initial CT showed a thin acute SDH on the right. Since the patient had no history of head trauma, his illness was diagnosed as nontraumatic acute SDH. Immediately thereafter, his condition deteriorated acutely and he became unresponsive. Repeat CT showed a marked increase of SDH with impending transtentorial herniation. Emergency right frontotemporal craniotomy was performed to remove the hematoma. Postoperatively, 3 dimensional CT angiography revealed a large aneurysm (22 mm in diameter) at the right MCA bifurcation. Aneurysm clipping was carried out on the same day. The postoperative course was satisfactory and he was discharged 3 weeks after surgery without any neurological deficits. Despite its rarity, rupture of an intracranial aneurysm should be kept in mind as a possible cause of nontraumatic acute SDH, because early diagnosis and definitive treatment can improve the prognosis. The possible mechanism of this condition is also discussed.
