Primary thunderclap headache.

Thunderclap headache is an uncommon type of headache, but recognition and diagnosis are important because of the possibility of a serious underlying brain disorder. In this chapter, primary thunderclap headache in relation to other primary headache disorders and secondary, symptomatic headache disorders are discussed. Most importantly, subarachnoid hemorrhage should be excluded. The first investigation is a computed tomography (CT) scan, and, if the CT scan is negative, investigation of the cerebrospinal fluid. Other symptomatic vascular causes are intracranial hemorrhage, cerebral venous sinus thrombosis, cervical artery dissection, or a reversible vasoconstriction syndrome. These and other serious underlying intracranial disorders should be detected by magnetic resonance imaging or the appropriate investigations. The remaining patients with thunderclap headache most likely represent a primary headache disorder, including migraine, primary cough headache, primary exertional headache, or primary headache associated with sexual activity. Within the group of primary headache disorders, primary thunderclap headache represents a distinct clinical entity; it is characterized by a sudden severe headache lasting from 1h up to 10 days and not attributed to another disorder. The pathogenesis of primary thunderclap headache is still not known, but the sympathetic nervous system may play an important role.