Thunderclap headache: symptom of unruptured cerebral aneurysm.

Many patients with a ruptured berry aneurysm report an intense sentinel headache of sudden onset in the weeks before rupture. Such headaches have been attributed to a leak of blood, which implies that partial rupture has occurred. A case is reported of a patient who had severe headaches which seemed to be caused by an unruptured cerebral aneurysm, accompanied by diffuse cerebral vasospasm. Headache episodes with the thunderclap profile may require angiography for diagnosis even if the cerebrospinal fluid is bloodless.