Thunderclap headache.

Abstract

Thunderclap headache refers to an excruciating headache of instantaneous onset. It occurs as suddenly and unexpectedly as a "clap of thunder." Patients with thunderclap headache may have normal neurologic examination results and normal computed tomographic brain scans, even if they have serious underlying pathology. This has created confusion regarding nosology and the nature and extent of the diagnostic evaluation, which this article discusses.