Unruptured cerebral aneurysm producing a thunderclap headache

A sudden and severe headache is the most common presentation of an acutely ruptured cerebral aneurysm. A similar headache in the absence of subarachno id blood has rarely been ascribed to an unruptured cerebral aneurysm, but m ay result from acute aneurysm expansion and indicate a high risk of future rupture. We present a patient who developed a sudden, severe, "thunderclap" headache, with no associated neurological deficit. Computed tomogram and l umbar cerebral spinal fluid obtained 5.5 hours after headache onset were ne gative for subarachnoid hemorrhage, The patient underwent cerebral angiogra phy which revealed a posterior communicating artery aneurysm with an associ ated daughter aneurysm. Craniotomy and clip obliteration of the aneurysm we re performed. The aneurysm dome was very thin and there was no evidence of recent or old hemorrhage. A "thunderclap" headache without subarachnoid hem orrhage may be an important harbinger of a cerebral aneurysm with the poten tial for future rupture, Early recognition and neurovascular imaging of ane urysms presenting in this rare fashion are warranted. Copyright (C) 2000 by W.B. Saunders Company.