Delayed angiographic detection of a ruptured basilar artery perforator aneurysm in diffuse initially angiographically occult subarachnoid hemorrhage: A case report and literature review.

Basilar artery perforator aneurysms (BAPAs) are uncommon and may remain occult on initial angiography because of their minute size and dynamic morphology. A 69-year-old man presented with sudden severe headache and mild drowsiness (Glasgow Coma Scale 14, World Federation of Neurosurgical Societies grade II). Computed tomography showed diffuse subarachnoid hemorrhage involving the basal cisterns and sylvian fissures with fourth ventricular intraventricular hemorrhage. Initial digital subtraction angiography (DSA) revealed no bleeding source. Although repeat DSA is generally performed approximately 1 week later at our institution, the diffuse and asymmetric aneurysmal-type hemorrhage pattern prompted earlier repeat DSA on hospital day 4. This demonstrated an approximately 1.7-mm fusiform-appearing aneurysm arising from a right basilar artery perforator just below the superior cerebellar artery. High-resolution vessel wall magnetic resonance imaging (MRI) and cone-beam computed tomography (CT) angiography were not performed. Conservative management was selected because of the minute distal perforator lesion and procedural risk. The patient was discharged on day 21 with a modified Rankin Scale score of 1, which remained unchanged at 3 months. This case emphasizes the importance of timely repeat DSA and consideration of adjunctive high-resolution imaging in diffuse initially DSA-negative subarachnoid hemorrhage.