Hemicrania Continua: An Update.

Background Hemicrania continua (HC) is not uncommon in clinical practice, and several large case series have been published in the recent past. Objectives This review provides an overview of the recent advancement in different aspects of HC. Methods We reviewed the articles published on HC in the last 2 decades. Results HC constitutes 1.7% of patients with headache in the clinics. It presents with unilateral continuous background pain with periodic exacerbations, usually accompanied by cranial autonomic features and restlessness. The continuous background headache is the most consistent and central feature of HC. Although the duration of exacerbations varies from a few seconds to a few weeks, the frequency ranges from >20 attacks/day to one attack in several months. The background pain is mild to moderate in intensity and does not hamper routine activity. Patients and physicians frequently ignore the basal pain, and a case of HC is misdiagnosed as other headaches, depending on the pattern of exacerbations. The exacerbation mimics several primary headaches and neuralgias. There are about 75 cases of secondary HC, due to 29 different pathologies. Although an absolute response to indomethacin is part of the diagnostic criteria, a subset of patients may respond to several other drugs. Headache reappears immediately on skipping a single dose of effective drug. Several surgical procedures have been tried in patients who are intolerant to indomethacin. Conclusion Misdiagnosis of HC is common. Continuous background pain and response to indomethacin are two essential features for the diagnosis of HC.