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Cluster headache (CH), also known as histamine headache, is a specific vascular headache syndrome and one of the most severe forms of headache. The underlying cause is still poorly understood but it is thought that the pain may be related to the dilation/alteration of blood vessels or to inflammation of nerves behind the eye.

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CH affects approximately 8-10% of all persons who suffer from headaches. They most commonly occur in men (six times more frequently than in women) between the ages of 20 and 40.

Cluster headaches are associated with dilation (widening) of blood vessels and inflammation of nerves behind the eye. In both cluster and migraine headaches blood vessels dilate, but in cluster headaches only the blood vessels behind the eyes pulsate. This leads some experts to believe that part of the pain is caused by dilation in branches of the carotid artery (a major artery that supplies the brain with blood). Some research suggests that a sensitivity to histamine, a chemical found in all body tissue, may play some role. Histamine opens blood vessels and can cause swollen membranes. Because such dilation appears to follow, not precede, pain, however, some researchers believe that some other process involving the central nervous system in the brain is more likely to be the primary cause.

Abnormalities in the Hypothalamus
The root cause of cluster headaches is unknown but researchers are zeroing in on areas in the brain where abnormalities occur. Evidence suggests that abnormalities in the hypothalamus of the brain may play a role. The hypothalamus is a complex brain structure located deep in the brain. It controls the pituitary gland (which is responsible for reproductive function) and also regulates body temperature, emotion, hunger, sleep, and the body's biologic rhythms (its circadian rhythms). In studying cluster headaches, researchers are particularly interested in the circadian rhythms because of the periodic nature of cluster attacks. Within the hypothalamus are small clusters of nerves that act like biologic clocks, the most important being one called the suprachiasmatic nuclei (SCN). It appears to help coordinate the body's activities (sleep/wake) with the environment (dark/light). Some studies support the idea that some impairment in this biologic pacemaker may cause these terrible attacks. (Cluster attacks often follow the seasonal increase in warmth and light, beginning in summer and ending in the fall.)

The hypothalamus is also involved in the regulation of many important hormones, including serotonin, norepinephrine, and cortisol (stress hormones), melatonin (related to sleep), and beta endorphins (involved with pain). As with other headaches, particularly migraines, alterations in serotonin are of particular interest. This neurotransmitting hormone (chemical messenger in the brain) affects, among other functions, well-being, sleep, and appetite. In cluster patients, there is some evidence of abnormal serotonin levels (although not as pronounced as in migraines). Some research suggested that serotonin may play an important role in the way circadian rhythms are expressed.

There are no abnormalities to be found upon a physical or laboratory investigation other than Horner's syndrome occasionally. In approximately 70% of patients with cluster headaches, the carotid artery is palpably tender at several points in the neck (Raskin and Prusiner, 1977).

Cluster headaches are observed more frequently among those who smoke and consume alcohol.

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Each headache episode generally lasts from fifteen minutes to three hours. Many such episodes may occur during a day. They tend to occur in cycles, often during the months of the year that are warmer and have more daylight. Persons who suffer from CH tend to be sociable, active and responsible and, for this reason, CH are sometimes called "the executive headache".

Only the CH victim can understand the excruciating pain and discomfort that characterize this disorder. Fortunately, only a small percentage of CH cases complain of the chronic form. Chronic CH is distinguished by its lack of a remission period lasting more than 14 days, or the absence of a remission period for more than one year.

The telltale signs of a cluster headache are distinct yet remarkably similar among CH sufferers everywhere. Here is a list of commonly reported symptoms associated with this condition:

• A piercing, stabbing pain on one side of the head and behind the eye
• Attacks occuring in clusters lasting several weeks, with a remission period of months or years between headache episodes
• Several headaches daily, recurring at the same time each day, often awakening one from sleep
• The inability to lay down or remain still
• Eye region becomes droopy, red and moist
• The nostril on the affected side becomes stuffed and runny
• There is the desire to pound one's head against a wall
• Feelings of dejection, anxiety and irritability.

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Many sufferers report that they have been to numerous doctors, neurologists and other specialists over a period of years, prior to being accurately diagnosed. In addition to their pain, they have incurred great frustration in seeking answers to their little-known condition, as well as untold expense, and have been subjected to a number of inappropriate treatments.

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Treatment of CH generally aims at prevention of the attacks. Since CH generally appears over several days at around the same time each day, it is possible to prevent these headaches by taking timely remedies.

Some migraine medications may be useful for reversing cluster headaches, although most are not effective for cluster patients.

Ergotamine. Dihydroergotamine (DHE) injections have stopped cluster attacks within five minutes in many patients. Ergotamine aerosols or ergotamine suppositories with caffeine may be useful. When using the aerosol the patient usually inhales two or three times. They should be sure to shake the canister vigorously and administer the spray while making an inhalation immediately after a forced exhalation. The patient should then hold the breath for several seconds before slowly exhaling. Proper administration can produce an effective response 80% of the time. (Oral and under-the-tongue preparations of ergotamine are ineffective because of the brevity of cluster attacks.)

Triptans. Triptans are migraine agents that are proving to have a role in stopping a cluster attack. Injections of sumatriptan have been used the longest. In one 1998 analysis of 2,031 attacks in 52 patients, it was successful in 88% attacks, and 42% of patients were pain-free within 15 minutes in over 90% of their attacks. (The nasal spray form is not very effective.) Side effects are common but are usually only considered to be unpleasant; they include nausea, odd sensations (e.g., tingling and numbness), dizziness, fatigue, sensations in the jaw and chest, and a fall in blood pressure. Other triptans, including rizatriptan (Maxalt) and zolmitriptan (Zomig), may prove to be good alternatives. In one study, zolmitriptan brought significant relief within 30 minutes for many episodic (but not chronic) cluster patients.

Local Anesthetics
Lidocaine, a local anesthetic, may be useful in nasal-spray or nasal-drop form for cluster attacks. Some reports suggest that it is helpful for about 60% of patients.

Methoxyflurane is an anesthetic. Inhaling about 10 to 15 drops applied to a cloth may help abort an attack.

Methysergide Methysergide, which is also used to prevent migraine, is believed to prevent cluster headaches by constricting blood vessels and reducing inflammation. It has serious side effects, however, and can be used only for brief periods, generally for the length of a cluster period.

Corticosteroids Corticosteroids, particularly prednisone and methylprednisolone, are used for short-term cluster therapy, due to potential serious side effects with longer-term use.

Calcium Channel Blockers Calcium channel blockers, typically used in treating cardiovascular conditions, are used to treat cluster headache episodes and chronic cluster headaches. They may work by blocking the release of neurotransmitters (chemicals in the brain that stimulate nerve cells) involved in causing pain.