Cluster headaches occur several times a day. They start suddenly, last for a limited time, and can be very painful.

Attacks occur cyclically. A bout of regular attacks, known as a cluster period, can last a few days, weeks, or months. This is followed by remission periods, during which there are no headaches.

Cluster headaches are not common. They are thought to affect about 1 in every 1,000 people. Six out of 10 cases involve men, and most of these are smokers. It usually starts after the age of 20 years.

Fast facts on cluster headaches

Here are some key points about cluster headaches. More detail is in the main article.

  • Cluster headaches normally affect one side of the head and the area around the eyes. There may be a reddened eye on the affected side of the head and a stuffy nose.
  • In northern countries, they are more common during the fall.
  • They affect around 1 in 1,000 people, and males are more likely to be affected.
  • A cluster often appears suddenly, lasts around an hour, then disappears suddenly.
  • During an attack, or cluster period, headaches happen frequently. During remission, the pain does not occur.

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There are a number of treatment options for cluster headaches.

There is no cure for cluster headaches, but drugs, such as sumatriptan, and other treatments, including oxygen therapy, can help reduce the incidence and severity of attacks.

Treatment aims to relieve some of the symptoms, shorten the periods of headaches, and reduce their frequency.

Over-the-counter (OTC) painkillers, such as aspirin or ibuprofen, are not effective, because the pain starts and finishes so rapidly that by the time the medication starts to work, the headache has probably gone.

Medications and treatments for cluster headaches aim either to prevent them or to act quickly.

Fast-acting treatments

Treatments that can provide rapid relief include:

Inhaling 100-percent oxygen: Breathing in oxygen through a mask at 7 to 10 liters per minute may bring significant relief within 15 minutes. It is not always practical to have an oxygen cylinder and regulator close at hand, but some small units are available. Oxygen therapy may only postpone symptoms, rather than alleviating them.

Injectable sumatriptan (Imitrex): Triptans are a class of drug that can treat migraines. Sumatriptan acts as an agonist for 5-hydroxytryptamine (5-HT) receptors. It can treat migraines, and it can bring rapid relief from cluster headaches. Zolmitriptan (Zomig) is a nasal spray, but it only works for some patients. The adult dose is a 6-milligram (mg) injection. Two injections can be taken in one 24-hour period, at least one hour apart.

People with uncontrolled hypertension (high blood pressure) or ischemic heart disease should not take this drug.

Dihydroergotamine: This is an effective pain reliever for some people. It can be taken intravenously or inhaled. A medical professional will need to give an intravenous dose. The inhaler form is effective but less fast-acting.

Octreotide (Sandostatin, Sandostatin LAR): These are synthetic versions of somatostatin, a brain hormone. It is injected. It is an effective treatment for cluster headaches and considered safe for those with hypertension or ischemic heart disease.

Local anesthetic nasal drops: Lidocaine (Xylocaine) is an effective treatment for cluster headaches.

Surgery: This may be an option if drug treatments do not work, or if the person cannot tolerate the medications. However, this is rare. It can only be performed once, and it is only suitable for those with pain on just one side of the head.

Surgical procedures include:

  • Conventional surgery: The surgeon cut part of the trigeminal nerve, which serves the area behind and around the eye. There are risks of damage to the eye.
  • Glycerol injection: Glycerol is injected into the facial nerves. This effective treatment is safer than other surgical procedures.

Possible future treatments

Some new treatment options are being investigated.

Occipital nerve stimulation: A small device is implanted over the occipital nerve. It sends impulses via electrodes. It appears to be well tolerated and safe to use.

Deep brain stimulation: This would involve implanting a stimulator in the hypothalamus, which appears to be linked to the timing of cluster headaches. This would change the electrical impulses in the brain.

Treatments that target the hypothalamus are considered by some researchers to be the most likely to succeed, and deep brain stimulation has been described as "at present the most attractive option" for patients who do not respond to other treatments.

However, further studies are needed to confirm its safety and effectiveness.

Preventive treatment

Most people with cluster headaches take short- and long-term medications. When each period of clusters is over, the short-term treatments stop, but the long-term ones may continue.

If attacks occur frequently, or if one lasts over 3 weeks, preventive treatments are recommended. The person will take the treatment the moment the headaches start, and continue until the period of headaches ends.

Short-term drugs

These are taken until one of the long-term medications start working.

Examples include:

  • Corticosteroids: These steroids, such as Prednisone, suppress inflammation. They are a fast-acting, preventive drug that can help those with new symptoms or those who have long periods of remission and short cluster periods.
  • Ergotamine (Ergomar): This temporarily narrows blood vessels throughout the body. It is taken at night before going to bed, either under the tongue or as a rectal suppository. Ergotamine cannot be taken with triptans. It should not be used for long periods, or if the person has poor circulation.
  • Anesthetic on the occipital nerve: Injecting anesthetic can numb this nerve, which is located at the back of the head. As a result, pain messages that travel along the nerve pathway are blocked. This treatment is stopped as soon as a long-term preventative medication starts to work.

Long-term drugs

Long-term drugs are taken throughout the cluster period. Some people may need more than one long-term medication.

  • Calcium channel blockers, such as verapamil (Calan, Verelan): These are taken during the cluster period and then gradually tapered off, although some people may need to use them long term. Side effects include constipation, nausea, tiredness, swollen ankles, low blood pressure (hypotension), and dizziness. If the dose is increased, regular heart monitoring will be needed.
  • Lithium carbonate, for example, lithium (Lithobid, Eskalith): Used to treat bipolar disorder, it is also effective in preventing chronic cluster headaches. Side effects include increased urination, diarrhea, and tremor. The intensity of side effects is usually linked to dosage, which the doctor can alter. Regular blood tests will check for possible kidney damage.
  • Anti-seizure medications, such as divalproex (Depakote) and topiramate (Topamax), are also effective long-term treatments for cluster headaches.

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Cluster headaches usually affect only one side of the head.

Symptoms include intense pain that starts rapidly, usually without warning. Pain is continuous rather than throbbing. It has been described as stabbing, sharp, burning, and penetrating.

It often starts around the eye, and it may then radiate to other parts of the head, including the face, neck, and shoulders. Pain may be present in a temple or a cheek. It remains on one side of the head.

There may also be:

  • restlessness
  • redness, swelling, watering in the eye on the side of the pain
  • stuffy, blocked, or runny nose on the pain side
  • pale skin
  • facial sweating
  • small pupil size
  • drooping of the eyelid on the pain side

The pain can waken a person during the night, and it may occur at the same time each night.

The individual may pace around during the episodes of pain, unable to stay still for long. If they do sit down, many may rock back and forth in an attempt to sooth the discomfort.

Each cluster can last from 15 minutes up to several hours, but not usually more than an hour. One to three clusters may occur each day.

After an attack, the pain will be gone, but the person may feel very tired.

It is not clear exactly why cluster headaches occur.

Research has found that during an attack there is more activity in the hypothalamus, an area of the brain that controls body temperature, hunger, and thirst.

It may be that this area of the brain releases chemicals that cause blood vessels to widen, resulting in a greater blood flow to the brain. This may cause the headaches.

Why this would happen is a mystery, but it is true that alcohol, a sudden rise in temperature, or exercising in hot weather may trigger attacks.

The cyclical nature of cluster headaches suggests that they may be linked to the biological clock, which is located in the hypothalamus.

Researchers have found that people who have cluster headaches often have unusual levels of melatonin and cortisol during an attack.

Apart from alcohol, cluster headaches are not linked to the consumption of any foods, and they have not been linked to mental stress or anxiety. Alcohol only acts as a trigger if a person is in the middle of a cluster period.

There may be a link between cluster headaches and some medications, such as nitroglycerin, which is used for the treatment of heart disease.

In northern countries, attacks tend to be more frequent during the fall and spring. Extreme variations in temperature can trigger an episode during an attack. The change in temperature is often linked to a rapid rise in body temperature.

Since the causes of cluster headaches remain unclear, there are no proven lifestyle measures for preventing them.

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Reducing alcohol intake can minimize cluster headache attacks.

The following may help reduce the risk of headaches:

  • Avoiding alcohol: At times when headaches are occurring, abstaining from alcohol may help reduce the number of headaches.
  • Avoiding some medications: Inhaled nitroglycerin causes blood vessels to dilate, or enlarge, and is linked to headache cluster attacks.
  • Avoiding exercising in hot weather: This can trigger cluster headaches.
  • Maintaining a regular body temperature: A sudden rise in body's temperature can trigger a headache in those who are susceptible.
  • Quit or avoid smoking: A significantly higher percentage of people with cluster headache are smokers, compared with the rest of the population. Although not proven, giving up smoking may help.
  • Maintain a regular sleep pattern: Cluster headaches have been associated with changes in the sleep routine.

Between 10 and 20 percent of people develop a resistance to the drugs that are normally used to treat cluster headaches.

They may find some relief from the following:

  • Melatonin may help treat attacks that occur at night.
  • Capsaicin, applied inside the nose, may help lessen the severity and frequency of headaches.

However, studies have not confirmed their effectiveness.

Cluster headaches can cause disruption to the daily routine, and this can lead to stress and depression. A counselor may help develop coping strategies.

Cluster headaches and migraines are both severe forms of headache, but they are different and need different treatment.

Before a migraine, a person will often experience an "aura," or visual disturbances, including flashing lights or zigzag lines. A migraine can last for up to 72 hours, and it commonly involves nausea, vomiting, and sensitivity to light.

A cluster headache starts and ends suddenly and it lasts a shorter time. It often features congestion, watery eyes, and a runny nose. It normally affects only one side of the head, and the eye that is watering is on the same side.

A person with a migraine prefers to lie down during an attack, but people with a cluster headaches say that lying down worsens the pain.

A cluster period usually lasts from 1 to 12 weeks. They often start at similar calendar moments, especially during springtime or fall.

Episodic cluster headaches: A series of searing headaches normally lasting from 1 week to 3 months (although in rare cases they can last up to a year), usually followed by 6 to 12 months of remission, with no pain. Then the period repeats itself.

Chronic cluster headaches: The cluster period can persist for several months, a year or longer. Periods of remission are short, lasting perhaps a month.

A cluster period may consist of:

  • daily occurrences, with symptoms appearing several times each day
  • one attack, lasting from 15 minutes to up to 3 hours
  • attacks that occur around the same time each day
  • attacks that are more likely to happen at night

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Many males who experience cluster headaches are smokers.

Risk factors for cluster headaches include:

  • Sex: Around 6o percent of people who have these headaches are male.
  • Age: Most cluster headaches start after the age of 20 years.
  • Ethnic ancestry: Cluster headaches are twice as common among people of African ancestry.
  • Smoking: Most men with cluster headaches are smokers.
  • Alcohol consumption: Alcohol appears to be a key trigger during a cluster period, but not during remission.
  • Genetics: If a close family member has cluster headaches, there is a higher chance of having them.

Anyone who has regular headaches should see a doctor. Treatment can often relieve symptoms, and it may be necessary to rule out any possible underlying causes.