Rupture of a previously documented asymptomatic aneurysm enhances the argument for prophylactic surgical intervention.

A case is presented of an incidentally discovered 6-mm aneurysm that was left untreated and subsequently produced a subarachnoid hemorrhage. The patient had no previous history of intracranial hemorrhage from any other source. A case of this type has not been previously documented in the literature. This experience points out the potential for catastrophe in small unruptured aneurysms found in patients without previous subarachnoid hemorrhage. The extremely low operative morbidity for repair of these types of lesions in otherwise healthy individuals would argue strongly for prophylactic surgery in properly selected patients.