Delayed appearance of basilar trunk small atypical aneurysms in nontraumatic, initially angiogram-negative subarachnoid hemorrhage: A report of three patients.

BackgroundRepeat angiography will identify vascular pathology in approximately 10% of cases following angiogram-negative subarachnoid hemorrhage (anSAH), but small atypical aneurysms of the basilar artery are very uncommon.ObjectiveTo report a case series of delayed appearance of nontraumatic basilar artery small atypical aneurysms.MethodsIRB approval was obtained for this retrospective case series and patient consent was waived.ResultsHerein we report three cases of spontaneous anSAH, all of whom had a negative digital subtraction angiogram (DSA) on admission and all of whom had appearance of a small atypical aneurysms of the upper basilar trunk/apex on follow-up imaging (two during the initial admission and one in a delayed fashion). All three patients were ultimately treated with flow diversion (although one patient underwent attempted coiling that was abandoned due to inability to catheterize the aneurysm).ConclusionThis report highlights the importance of a repeat DSA in cases of anSAH as well as the importance of scrutinizing the basilar trunk for these very small atypical aneurysms that may go unnoticed.