Cluster headache is a primary form of headache that is characterized by the manner in which the attacks occur, which are precisely “clustered” in so-called “active periods” lasting up to several months, interspersed with phases of complete remission.
Cluster headache is an infrequent form of headache that predominantly affects men in adulthood (the male:female ratio is about 3-4:1), particularly between the ages of 30 and 40.