Hemicrania continua. Unquestionably a trigeminal autonomic cephalalgia

Hemicrania continua (HC) is a well-known primary headache. The present version of the International Classification of Headache Disorders lists HC in the "other primary headaches" group. However, evidence has emerged demonstrating that HC is a phenotype that belongs to the trigeminal autonomic cephalalgias together with cluster headache, paroxysmal hemicrania (PH), and short-lasting, unilateral neuralgiform headache attacks with conjunctival injection and tearing. This is supported by a common general clinical picture - paroxysmal, fluctuating, unilateral, side-locked headaches located to the ocular, frontal, and/or temporal regions, accompanied by ipsilateral autonomic dysfunctions including for example, tearing and conjunctival injection. Apart from the remarkable clinical similarities, the absolute and incomparable effect of indomethacin in HC parallels the effect of this drug in PH, suggesting a shared core pathogenesis. Finally, neuroimage findings demonstrate a posterior hypothalamic activation in HC similarly to cluster headache, PH, and short-lasting, unilateral neuralgiform headache attacks with conjunctival injection and tearing. Taken together, data indicate that HC is certainly a type of trigeminal autonomic cephalalgia that should no longer be placed in a group of miscellaneous primary headache disorders.