Classification and Clinical Features

Cluster headache (CH) and other trigeminal autonomic cephalgias (TACs) are primary headaches. Their clinical diagnosis depends on the classification system of the International Headache Society (IHS). TACs are a group of relatively uncommon headaches that share the clinical features of head pain, which is usually unilateral and severe, and prominent cranial autonomic features, which are generally ipsilateral to the pain. Autonomic symptoms include ptosis, miosis, conjunctival injection, tearing, facial and frontal sweating, nasal obstruction, rhinorrhea, and increased intraocular pressure. Characteristically, especially in CH, patients have a very restless behavior with great agitation. Duration of attacks and response to indomethacin are the principal characteristics useful to distinguish each form. This group of headaches includes CH, paroxysmal hemicrania (PH), short-lasting unilateral neuralgiform headache attacks (SUN) with its variants, and hemicrania continua (HC).