Multiple intracranial aneurysms in identical twins.

Familial intracranial aneurysms are well documented, with the highest association occurring among siblings. Five pairs of identical twins with subarachnoid hemorrhage have been previously reported. We present the sixth set of identical twins with multiple aneurysms. These cases represent the first report in the literature of multiple mirror aneurysms in identical twins. One twin presented with subarachnoid hemorrhage. Her sister, who was asymptomatic, had elective angiography which demonstrated multiple aneurysms in locations identical to her sister's aneurysms. In families in which a twin presents with subarachnoid hemorrhage, it is appropriate to recommend angiography to the asymptomatic twin.