Cluster headache.

Cluster headache is a rare condition that predominantly affects older men. The diagnosis is based on the history and clinical characteristics, which are distinctive. The headache is always unilateral, excruciating and, most uniquely, occurs in timed attacks, called "clusters." The etiology is unknown, but disturbances in the hippocampal areas controlling circadian rhythm may contribute to cluster headache. Various treatments to relieve individual attacks and to shorten active cluster periods have been used, including systemic corticosteroids, lithium, ergotamine and calcium channel blockers. Patient education and individualized treatment are important elements of the management plan.