A cluster headache is one of the most painful types of headache. It's also distinctive in ways other than the severity of the pain. A primary feature of cluster headache is that the attacks occur in cyclical patterns, or clusters, giving the condition its name.
Bouts of frequent attacks in cluster periods may last from weeks to months, followed by remission periods when the headache attacks stop completely. The pattern varies from one person to another but most people have one cluster period a year. During remission, no headaches occur for months and sometimes even years. Fortunately, cluster headache is rare. Cluster headache can affect people at any age but is most common between ages 20 and 40 and is more common in men .
Although cluster headache attacks are extremely painful, they're not life-threatening. Treatments can help make the attacks shorter and less severe. In addition, preventive medications can help reduce the number of headaches.

Signs and symptoms
A cluster headache strikes quickly, usually without warning. Within minutes excruciating pain develops. The pain typically develops on the same side of your head throughout a cluster period, and often the headaches remain on that side throughout your life. Less frequently, the pain may switch to the opposite side of your head in the next cluster period. Rarely, the pain switches sides from one attack to another. The pain of a cluster headache is often described as sharp, penetrating or burning.

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Causes
Unlike migraine and tension headache, cluster headache generally isn't associated with triggers such as foods, hormonal changes or stress, although some people report that once a cluster period begins consumption of alcohol can trigger a splitting headache within minutes.
Other possible triggers include the use of medications such as nitroglycerin. The beginning of a cluster period often follows occasions when normal sleep patterns are disrupted, such as during a vacation or when starting a new job or work shift. Some people with cluster headache also have sleep apnea, a condition in which the walls of a person's throat collapse momentarily, obstructing the sleeper's breathing repeatedly during the night.

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Treatment
Because the pain of a cluster headache comes on suddenly and may subside within a short time, over-the-counter pain relievers such as aspirin or ibuprofen aren't effective. The headache is usually gone before the drug starts working. Fortunately, other types of acute medication can provide some pain relief. Treatment of cluster headache is focused more on prevention, with more medication options available to choose from. Acute treatments include:

• Oxygen. Briefly inhaling percent oxygen through a mask at a rate of 6 to 8 liters a minute provides dramatic relief for most who use it. Occasionally, a higher flow rate may be more effective. The effects of this safe, inexpensive procedure can be felt within 15 minutes. The major drawback of oxygen is the need to carry an oxygen cylinder and regulator with you, which can make the treatment inconvenient and inaccessible at times. Small, portable units are available, but some people still find them impractical. Sometimes, oxygen may only delay rather than stop the attack, and pain may return.
• Sumatriptan. The injectable form of sumatriptan (Imitrex), which is commonly used to treat migraine, is also an effective acute treatment for cluster headache. Some people may benefit from using sumatriptan in nasal spray form, but for most this is not as effective as an injection. Sumatriptan isn't recommended for people with uncontrolled high blood pressure or ischemic heart disease. Another triptan medication, zolmitriptan (Zomig), can be taken orally for relief of cluster headache. Although oral zolmitriptan isn't as effective as injectable sumatriptan, it may be an option for people who can't tolerate other forms of acute treatment. Zolmitriptan also is available in nasal spray form.
• Dihydroergotamine. This ergot derivative is available in intravenous, injectable and inhaler forms. Dihydroergotamine (D.H.E. 45, Migranal) is an effective pain reliever for some people with cluster headache. When administered intravenously, the drug requires you to go to a hospital or doctor's office to have an intravenous (IV) line placed. The inhaler form of the drug works more slowly. The dosage must be limited to avoid side effects, especially nausea.
• Octreotide (Sandostatin, Sandostatin LAR). This drug, a synthetic version of the brain hormone somatostatin, has traditionally been used to control severe diarrhea. However, some studies have shown that the injectable form is an effective treatment for cluster headache and is safe for people with high blood pressure and ischemic heart disease.
• Local anesthetics. The numbing effect of local anesthetics, such as lidocaine (Xylocaine), may be effective against cluster headache pain when used in the form of nasal drops. Surgery Rarely, surgery is recommended for people with chronic cluster headache who don't respond well to aggressive treatment or who can't tolerate the medications or their side effects. Candidates for surgery must have headaches only on one side of the head because the surgery can be performed only once. People with headaches that alternate sides of the head risk the chance that the procedure will be unsuccessful.