Anterior Communicating Aneurysm Missed at Angiography: Report of Two Cases Treated Surgically

: We report two young adults with definite clinical and computed tomographic (CT) signs of subarachnoid hemorrhage in whom initial angiography showed spasm of the anterior portion of the circle of Willis, but no aneurysm. Repeat angiography some days later, when the vascular spasm had cleared, was likewise negative. In both patients, operation revealed an anterior communicating artery aneurysm, which was successfully excluded from the circulation. Our aims in reporting this unusual experience are to stress the practical importance of CT scanning in the diagnosis and treatment of subarachnoid hemorrhage and to discuss the decision to operate.