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Cluster headaches occur in cyclical patterns or clusters, which gives the condition its name. Cluster headache is one of the most painful types of headache.
Cluster headache commonly awakens you in the middle of the night with intense pain in or around one eye on one side of your head.
Bouts of frequent attacks, known as cluster periods, may last from weeks to months, usually followed by remission periods when the headache attacks stop completely. During remission, no headaches occur for months and sometimes even years.
Fortunately, cluster headache is rare and not life-threatening. Treatments can help make cluster headache attacks shorter and less severe. In addition, medications can help reduce the number of cluster headaches.
The exact cause of cluster headaches is unknown, but abnormalities in the hypothalamus likely play a role. Cluster attacks usually occur with clocklike regularity during a 24-hour day, and the cycle of cluster periods often follows the seasons of the year.
These patterns suggest that the body’s biological clock is involved. In humans, the biological clock is located in the hypothalamus, which lies deep in the center of your brain.
Abnormalities of the hypothalamus may explain the timing and cyclical nature of cluster headache. Imaging studies have detected increased activity in the hypothalamus during the course of a cluster headache.
Unlike migraine and tension headache, cluster headache generally isn’t associated with triggers, such as foods, hormonal changes or stress. Some people experience an aura or nausea similar to those experienced with migraine headaches.
Once a cluster period begins, however, consumption of alcohol can quickly trigger a splitting headache. For this reason, many people with cluster headache avoid alcohol for the duration of a cluster period.
Other possible triggers include the use of medications such as nitroglycerin, a drug used to treat heart disease.
A cluster headache strikes quickly, usually without warning. Common signs and symptoms include:
- Excruciating pain, generally located in or around one eye, but may radiate to other areas of your face, head, neck and shoulders
- One-sided pain
- Excessive tearing
- Redness in your eye on the affected side
- Stuffy or runny nasal passage in your nostril on the affected side of your face
- Sweaty, pale skin (pallor) on your face
- Swelling around your eye on the affected side of your face
- Drooping eyelid
The pain of a cluster headache is often described as sharp, penetrating or burning. People with this condition say that the pain feels like a hot poker being stuck in the eye or that the eye is being pushed out of its socket.
People with cluster headache appear restless. They may pace or sit through the attack. In contrast to people with migraine, people with cluster headache usually avoid lying down during an attack because this position seems to increase the pain.
Some migraine-like symptoms — including nausea, sensitivity to light and sound, and aura — may occur with a cluster headache, though usually on one side.
Cluster period characteristics
A cluster period generally lasts from six to 12 weeks. The starting date and the duration of each cluster period may be consistent from period to period. For example, cluster periods may occur seasonally, such as every spring or every fall.
Most people have episodic cluster headaches. In episodic cluster headaches, the cluster headaches occur for one week to a year, followed by a pain-free remission period that may last as long as 12 months before another cluster headache develops.
Chronic cluster periods may continue for more than a year, or pain-free periods may last less than one month.
During a cluster period:
- Headaches usually occur every day, sometimes several times a day.
- A single attack may last from 15 minutes to three hours.
- The attacks often happen at the same time within each 24-hour day.
- The majority of attacks occur at night, usually one to two hours after you go to bed.
The pain usually ends as suddenly as it begins, with rapidly decreasing intensity. After attacks, most people are completely free from pain, but exhausted.
When to see a doctor
See your doctor if you’ve just started to experience cluster headaches to rule out other disorders and to find the most effective treatment.
Headache pain, even when severe, usually isn’t the result of an underlying disease, but headaches may occasionally indicate a serious underlying medical condition, such as a brain tumor or rupture of a weakened blood vessel (aneurysm).
Additionally, if you have a history of headaches, see your doctor if the pattern changes or your headaches suddenly feel different.
Seek emergency care if you have any of these signs and symptoms:
- Abrupt, severe headache, often like a thunderclap
- Headache with a fever, nausea or vomiting, stiff neck, mental confusion, seizures, numbness, or speaking difficulties, which may indicate a number of problems, including stroke, meningitis, encephalitis or brain tumor
- Headache after a head injury, even if it’s a minor fall or bump, especially if it gets worse
- A sudden, severe headache unlike any other headache you’ve experienced
- Headache that gets progressively worse over days and changes in pattern