Clinical spectrum of thunderclap headache.

Headaches of the thunderclap variety become severe in intensity within seconds to a minute of onset. Patients with thunderclap headache are to be evaluated in an emergent fashion as many of the underlying causes are associated with significant morbidity and mortality. Although subarachnoid hemorrhage is usually the initial consideration, a multitude of other etiologies have been identified and are discussed herein. In accordance with the increased utilization of cerebral imaging, availability of noninvasive techniques to image the cerebral vasculature and interest in identifying causes of thunderclap headaches, the list of potential causes is growing rapidly. Included in this growth are the reversible cerebral vasoconstriction syndromes, terminology recently introduced to unify several disorders all presenting with thunderclap headache and similar diagnostic findings including reversible vasoconstriction of the intracranial arteries.