Subarachnoid hemorrhage from a basilar artery perforator pseudoaneurysm: a rare challenging lesion in the posterior circulation. Illustrative case.

backgroundBasilar artery perforator pseudoaneurysms are rare vascular lesions that present significant diagnostic and therapeutic challenges. Their management remains unstandardized, with limited evidence guiding treatment decisions. OBSERVATIONS: The authors report the case of a 74-year-old man with multiple comorbidities who presented with subarachnoid hemorrhage (SAH). Initial CT/CT angiography revealed diffuse SAH with intraventricular extension. Digital subtraction angiography demonstrated a pseudoaneurysm arising from a basilar perforator. The absence of an accessible inflow combined with the prohibitive procedural and surgical risks, neither endovascular embolization nor open surgery was attempted. Thus, conservative management was pursued, and repeat angiography on postoperative day 2 revealed spontaneous thrombosis of the pseudoaneurysm. Despite radiographic resolution, the patient's course was complicated by vasospasm, infarction, and persistent coma, resulting in the patient's death on day 21. LESSONS: Basilar perforator pseudoaneurysms are rare lesions that may be occult on initial imaging; repeat angiography is essential when posterior-circulation SAH lacks an identified source. Endovascular treatment risks perforator occlusion or require antiplatelets in an acute SAH setting. Open surgery also has its limitations with deep exposure, lack of proximal/distal control, and intraoperative rupture. Since neither route is safely feasible, conservative management with intensive neurocritical care and serial imaging is often the management approach. Unfortunately, radiographic thrombosis does not ensure recovery. https://thejns.org/doi/10.3171/CASE25779.