Trigeminal autonomic cephalalgias: paroxysmal hemicrania, SUNCT/SUNA, and hemicrania continua

The trigeminal autonomic cephalalgias (TACs) are a group of primary headache disorders that include cluster headache (CH), paroxysmal hemicrania (PH), and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing/cranial autonomic features (SUNCT/SUNA). Hemicrania continua (HC) is often included with this group, although the second edition of The International Classification of Headache Disorders did not link the entities. Trigeminal autonomic cephalalgias are generally characterized by relatively short-lasting attacks of severe pain and lateralized associated features including the pain, cranial autonomic symptoms, and where present, migrainous symptoms, such as photophobia. Paroxysmal hemicrania has intermediate duration and intermediate attack frequency. Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing has the shortest attack duration and the highest attack frequency. Hemicrania continua has a continuous pain with exacerbations that can include cranial autonomic symptoms as part of the phenotype. The syndromes share much in their pathophysiology and investigation paths; however, their treatment is distinct, so that the accurate differentiation is important for optimal management.