Could you tell me what happens during cluster headaches?

Good question: Scientists do not know exactly what causes cluster headaches, but they appear to be related to the body's sudden release of histamine or serotonin. A problem in a small area at the base of the brain called the hypothalamus may be involved.http://www.nlm.nih.gov/medlineplus/ency/article/000786.htm.

Cluster headache: Cluster headache is the most painful of all the primary headache disorders. Because of the intense pain, cluster patients often pace the floor or bang their heads during headache episodes while rubbing or holding the painful site in any attempt to distract themselves from the pain. They are agitated and restless in contrast to a migraineur who prefers to lie down, usually in a darkened room.