Nonaneurysmal thunderclap headache with diffuse, multifocal, segmental, and reversible vasospasm

Objective. To highlight the clinical profiles and angiographic findings of two patients with recurrent thunderclap headache (TCH) without subarachnoid hemorrhage (SAH) and to present modified diagnostic criteria for this unus ual syndrome. Background. TCH may be a benign recurrent headache disorder o r it may represent a serious underlying process such as SAH or venous sinus thrombosis. The pathophysiology of this disorder in the absence of underly ing pathology is not well understood and its potential angiographic feature s are not well appreciated. Methods. Two case descriptions with illustrativ e angiography. Results. Both cases demonstrated the potential for reversibl e intracranial vasospasm without intracranial aneurysm or SAH and a benign clinical outcome. Conclusions. Primary TCH has a distinctive clinical and a ngiographic profile and must be distinguished from central nervous system v asculitis and SAH.