Rebleeding and spontaneous resolution of an initially angiography-negative basilar artery perforator aneurysm: A case report.

Basilar artery perforator aneurysms (BAPAs) are rare causes of spontaneous subarachnoid hemorrhage and may be occult on initial vascular imaging. We report a 55-year-old woman who presented with headache and was found to have subarachnoid hemorrhage (modified Fisher grade 3, Hunt-Hess grade 2). Initial computed tomography angiography, same-day digital subtraction angiography, and follow-up magnetic resonance angiography on hospital day 4 were negative. On hospital day 6, her mental status deteriorated to stupor, and computed tomography demonstrated a new hemorrhage in the interpeduncular and suprasellar cisterns with hydrocephalus, suggesting rebleeding. Emergency repeat digital subtraction angiography demonstrated a small aneurysmal lesion with pseudoaneurysm-like morphology arising from a left basilar artery perforator. Endovascular treatment, including stenting, was considered; however, conservative management was chosen because of concerns regarding thromboembolic events and perforator infarction. External ventricular drainage was performed, and conservative management was continued. Her mental status gradually improved, and follow-up digital subtraction angiography performed 6 and 18 days after lesion identification demonstrated complete disappearance of the lesion. Follow-up magnetic resonance angiography at 4 months and 1 year after discharge revealed no recurrence. This case highlights that repeat angiography should be considered in initially angiography-negative subarachnoid hemorrhage and that carefully selected basilar perforator lesions may resolve with close conservative management, even after rebleeding.