[A case of internal carotid-posterior communicating artery aneurysm presenting pure acute subdural hematoma].

The incidence of acute subdural hematoma (SDH) due to a ruptured intracranial aneurysm varies from 0.5% to 7.9% of all intracranial aneurysms. Pure acute SDH without subarachnoid hemorrhage (SAH) is rare. According to the literature, only 18 cases (including our case) of pure acute SDH identified by CT scan have been reported. Here we report a case of an internal carotid-posterior communicating artery (IC-PC) aneurysm presenting pure acute SDH identified by CT. We summarize the 18 reported cases. A 55-year-old female experienced severe headache on October 9, 1999, which did not improve after medication. Four days later, left ptosis began. She was admitted to the department of ophthalmology to treat oculomotor nerve paresis. A computed tomography (CT) scan obtained on admission, revealed no obvious abnormality. She was treated by hormonal therapy, but her symptoms continued. Ten days later, she suddenly lost consciousness and was transferred to our hospital. Although the CT scan revealed a thick left SDH with marked midline shift, SAH was absent. Her neurological state was Hunt & Kosnik grade IV. A left carotid angiogram revealed an IC-PC aneurysm with active extravasation. The patient was taken to the operating room for emergency removal of the SDH and aneurysmal neck clipping. During the operation, adhesion between the aneurysmal dome and the arachnoid was observed, but subarachnoid hemorrhage was not identified at all. The aneurysm was successfully clipped. Postoperatively, her consciousness improved immediately. In this case, the pure acute SDH identified by CT was responsible for causing the direct hemorrhage into the subdural space via an adhesive lesion.