Appearance of an anterior communicating artery aneurysm during vasospasm treatment after angiogram-negative subarachnoid hemorrhage: A case report

Background: Initial angiography may not identify a bleeding source in some subarachnoid hemorrhage (SAH) cases. We report an instructive case of initially angiogram-negative SAH where an anterior communicating artery aneurysm became apparent during treatment for vasospasm, subsequently requiring successful endovascular embolization. Case Description: A woman in her 60s presented with diffuse SAH (Fisher group 3); initial computed tomography angiography (CTA) and digital subtraction angiography were negative for aneurysms. Symptomatic vasospasm developed on day 4, and treatment including cilostazol and fasudil was initiated. A repeat CTA on day 8 revealed the aneurysm. Conclusion: This case underscores that even with negative initial angiography, an underlying aneurysm should be strongly suspected in patients with diffuse SAH or subsequent vasospasm. It highlights the critical importance of meticulous follow-up and appropriately timed, high-quality imaging re-evaluation, which can lead to accurate diagnosis and favorable outcomes.