Characteristics of a Pure Acute Subdural Hematoma Caused by Intracranial Aneurysm Rupture: A Case Report and Review of Literature.

Pure acute subdural hematomas (ASDHs) due to ruptured aneurysms without subarachnoid or intracerebral hemorrhage are rare. We report the case of a 26-year-old female who presented with a pure ASDH caused by a ruptured distal anterior cerebral artery (ACA). The patient complained of sudden headache and vomiting and was transferred to our hospital. On the ambulance journey to the hospital, her consciousness level decreased suddenly just after experiencing additional pain in the head. At admission, the consciousness level was 4 points on the Glasgow coma scale with bilateral pupil dilatation. Computed tomography (CT) and CT angiography showed a left ASDH without subarachnoid hemorrhage (SAH) and a distal ACA aneurysm. Emergent hematoma evacuation was performed, but SAH and the bleeding point were not observed. Therefore, coil embolization for the distal ACA aneurysm was performed after an emergent operation. During embolization, intraoperative rupture was observed. The contrast media was seen up to the convexity subdural space along the falx. Extravasation ceased after intraaneurysmal coil embolization. Consequently, the rupture of the distal ACA aneurysm was diagnosed as the cause of the pure ASDH. The patient received additional coil embolization due to recanalization of the aneurysm without rebleeding 44 days after admission and was transferred to a rehabilitation hospital 55 days after admission to our hospital with a score of 4 on the modified ranking scale. From the reviews of 56 patients from 32 studies, including our case, we determine that an ACA aneurysm could show the distant hematomas located far from the site of a ruptured aneurysm compared with a ruptured aneurysm located in the internal carotid and middle cerebral arteries. Distant hematoma location could also lead to delayed diagnosis of aneurysms and lead to rebleeding and poor outcomes. Aneurysm rupture diagnoses should receive special attention, especially for ACA aneurysms, as the hematoma may be located far from the rupture site.