Classification, diagnostic criteria, and epidemiology
The trigeminal autonomic cephalalgias (TACs), including cluster headache, paroxysmal hemicrania, SUNCT (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing), SUNA (with cranial autonomic symptoms), and hemicrania continua, belong to the primary headaches. They are characterized by severe unilateral headache attacks in association with ipsilateral cranial autonomic features. Cluster headache is the most frequent of the TACs. The other TACs are rare, but epidemiological data are scarce and variable. The various types of TAC are distinguished not only by differences in attack frequency and duration, but also by differences with respect to treatment response. The typical headache syndromes, fulfilling the International Classification of Headache Disorders-3 criteria, have also been described in association with other disorders and imaging is required to exclude intracranial pathology in all newly diagnosed patients.