Thunderclap headache

In a patient presenting with severe headache, differentiating an idiopathic primary headache from a symptomatic secondary headache is the first task of the provider. The failure to recognize a secondary cause for the severe headache can result in significant increases in morbidity and mortality. The term thunderclap headache (TCH) refers to a sudden onset of intense and explosive headache, a phenotype recognized to be associated with multiple pathologies including aneurysmal subarachnoid hemorrhage. This chapter gives a critical review of the evidence by discussing the risks of secondary TCH and the differential diagnosis of TCH. The methods of diagnosis involving lumbar puncture (LP), advanced noninvasive neuroimaging and invasive angiography are discussed with reference to their necessity in diagnosing TCH. In individuals with delayed or atypical presentations and in those with negative CT and LP, brain MRI and noninvasive angiography should be considered. The prevalent nature of incidental unruptured intracranial aneurysms is an important factor often cited as reason to avoid advanced vascular imaging. Objective biomarkers and risk stratification tools are needed to better assess an unruptured intracranial aneurysm discovered in the evaluation of TCH. Future studies should also specifically assess the risk of CAD, CVST, RCVS and others among patients presenting with TCH, and explore the costs against potential benefits of routinely screening for these conditions.