Cluster headaches are among the most painful, and least common, of all headaches. The pain can be so excruciating that they are sometimes referred to as "suicide headaches." Their signature is a pattern of periodic cycles ("clusters") of headache attacks, which may be either:
- Episodic. Attacks occur regularly for 1 week to 1 year, separated by long pain-free periods that last at least 1 month. Between 80 - 90% of patients have episodic cycles. A significant number of people who experience a first cluster attack do not have another one.
- Chronic. Attacks occur regularly for more than 1 year, with pain-free periods lasting less than 1 month. Between 10 - 20% of patients have chronic cluster headaches. The chronic form is very difficult to treat.
Typical Cluster Cycles
Timing of an Attack. Cluster headache attacks tend to occur with great regularity at the same time of day. (For this reason, cluster headaches are sometimes referred to as "alarm clock" headaches.) About 75% of attacks occur between 9 p.m. - 10 a.m. Attacks may also peak between 1 - 3 p.m.
Duration of an Attack. A single cluster attack is usually brief but extremely painful, lasting about 15 minutes - 1.5 hours if left untreated.
Number of Attacks per Day. During an active cycle, people can experience as few as 1 attack every other day to as many as 8 attacks a day.
Duration of Cycles. Attack cycles typically last 6 - 12 weeks with remissions lasting up to 1 year. In the chronic form, attacks are ongoing, and there is little remission. Attacks cycles tend to occur seasonally, most often in the spring and autumn.
Primary Headaches That Resemble Cluster Headaches
Chronic Paroxysmal Hemicrania. Chronic paroxysmal hemicrania is a close relative of cluster headache and very similar. It causes multiple, short, and severe daily headaches with similar symptoms. Unlike cluster headaches, the attacks are shorter (1 - 2 minutes) and more frequent (occurring an average of 15 times a day). This headache is even rarer than cluster headache, tends to occur in women, and always responds to treatment with the drug indomethacin (Indocin).
Hemicrania Continua. Hemicrania continua occurs mostly in women. The patient generally experiences continuous low-level headache always on one side of the face. Periodic attacks can last days to weeks, which can be mild to severe, and may resemble migraines. (About 10% of patients experience remissions.) The headache can usually be treated successfully with indomethacin, which helps differentiate it from cluster and migraine headaches.
SUNCT Syndrome. A disorder called SUNCT syndrome (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing) causes stabbing or burning eye pain that may resemble cluster headaches, but attacks are very brief (lasting about a minute) and may occur more than 100 times per day. Red and watery eyes, sweating forehead, and congestion are typical. This rare headache is more common in men and does not respond to other headache treatments.
Review Date: 09/29/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.