ABSTRACT
Trigeminal autonomic cephalgias (TACs), a term coined by Goadsby and Lipton (1), represent a group of primary headache disorders manifested by pain in the somatic distribution of the trigeminal nerve and by autonomic signs that reflect activation of the cranial parasympathetic pathways. The headache disorders within this group include cluster headache, paroxysmal hemicrania, and the short-lasting unilateral neuralgiform pain with conjunctival injection and tearing (SUNCT) syndrome. The TACs are characterized by discrete, stereotyped, and relatively short-lasting (seconds to three hours) episodes of severe unilateral pain that is often confined or maximal in the orbital/periorbital region. The attacks are separated by pain-free intervals, but often recur on a daily basis either continuously (chronic) or for a defined period of time (episodic) with intervening remission periods. They are differentiated from each other based on the duration of the individual attacks, the daily frequency of attacks, and the response to various medications (Fig. 1, Table 1). Hemicrania continua is a continuous headache that should be considered in the differential diagnosis of other chronic daily headache disorders of longer duration (more than four hours). These disorders must also be differentiated from a variety of other primary headache disorders and organic causes that can mimic the phenotype of any one of these disorders. These disorders are highly disabling and eminently treatable, underscoring the importance of an accurate diagnosis.
