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 unusual syndrome. Background. TCH may be a benign recurrent headache disorder or it may represent a serious underlying process such as SAH or venous sinus thrombosis. The pathophysiology of this disorder in the absence of underlying pathology is not well understood and its potential angiographic features are not well appreciated. Methods. Two case descriptions with illustrative angiography. Results. Both cases demonstrated the potential for reversible intracranial vasospasm without intracranial aneurysm or SAH and a benign clinical outcome. Conclusions. Primary TCH has a distinctive clinical and angiographic profile and must be distinguished from central nervous system vasulitis and SAH.