Paroxysmal hemicrania, SUNCT, and hemicrania continua.

The trigeminal autonomic cephalalgias (TACs) are a group of primary headache disorders characterized by unilateral pain in the somatic distribution of the trigeminal nerve and ipsilateral autonomic signs, which reflect activation of the cranial parasympathetic pathway. The group includes cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing. Hemicrania continua was previously classified as one of the TACs. Despite their common elements, individually these headaches differ with respect to attack duration, frequency, and response to indomethacin.