Cluster Headaches

Intense and often excruciating unilateral pain that is accompanied by one-sided facial symptoms such as flushing, congestion, and swollen eye, may be cluster headache. The pain is described as stabbing or knifelike, and it radiates toward the eye or jaw from the temple.

The name “cluster headache” comes from the frequency and course of the condition. These headaches occur in distinct patterns of close and frequent attacks, or clusters, recurring over two weeks to three months, followed by headache-free “remission” periods that can last anywhere from a month to several years.

About half of cluster headache sufferers experience a headache daily during a cluster episode, and an estimated 33 percent experience two or more headaches in a 24-hour period. The headaches themselves often occur at the same time each day and last 15 minutes to three hours, with an average headache duration of 45 minutes. Many experience headache waking them one to two hours after falling asleep.

Cluster headache attacks that occur in episodes of one week to a year, but are separated by a remission period of a month or longer, are called episodic cluster headache. Some people with episodic cluster headache may only experience one attack a year, at the same time each year. However, for between 10 and 15 percent of cluster headache sufferers, the condition is chronic — meaning that they have cluster attacks that last longer than a year with no remission, or they experience remission periods of less than one month.

Unlike most headache disorders, cluster headache occurs more frequently in men than in women. Men are three to four times more likely to develop cluster headaches, and the condition typically makes its first appearance between the ages of 20 and 40 years old. Cluster headache is relatively rare, impacting less than 1 of every 1,000 adults, according to the World Health Organization.

Making the Diagnosis

Cluster headache is one of a group of headache types known clinically as trigeminal autonomic cephalgias, or TACs. These headaches involve the trigeminal nerve (fifth cranial nerve), the largest nerve of the head that is the gatekeeper for the nerve conduction that supplies sensation to the face.

No one knows for sure what triggers the pain of cluster headache. It may be caused by a disorder of the brain's pacemakers, and recent observations suggest that there are abnormalities in the structure and connections in the part of the brain called the hypothalamus in individuals who suffer with this condition.

This region of the brain is also responsible for many of the body's autonomic, or involuntary, nervous system functions, and so it is not surprising that these headaches are accompanied by a chain reaction of autonomic responses including facial flushing, tearing of the eye, and drooping of the eyelid.

Sometimes, an undiagnosed cluster headache sufferer will seek help for the facial symptoms of the disorder. A dentist or ear-nose-throat (ENT) specialist may be consulted about recurring tooth, jaw, and/or sinus pain.

Because the pain of cluster headache is on one side of the head, it can be misdiagnosed as migraine. The severity and the pattern of the headache pain can help distinguish cluster headache from migraine. In addition, cluster headache can cause a general sense of restlessness and agitation, while migraineurs, in contrast, typically feel the need to withdraw and rest in a darkened quiet room.

The International Headache Society (IHS) defines cluster headache as five or more episodes of head pain that meet the following diagnostic criteria:

  • Severe or very severe one-sided pain in or above the eye or in the temporal (temple) area of the head that lasts 15 minutes to three hours (if left untreated)

  • The headache is accompanied by at least one of the following symptoms:

    • Swelling and redness and/or tearing of the eye on the same side as the head pain

    • Congestion and/or runny nose on the same side as the head pain

    • Swelling of the eyelid that is on the same side as the head pain

    • Sweating of the face and forehead on the same side as the head pain

    • Constriction of the pupil and/or drooping of the eyelid on the same side as the head pain

    • A sense of restlessness or agitation

  • Attacks have a frequency from one every other day to eight per day

  • Pain is not attributable to another medical disorder

It's important to note that although the above criteria places a time limit on an untreated headache episode, the IHS also says that up to half of attacks may be of shorter or longer duration, and some of these may also be less severe. In addition, the frequency of attacks (i.e., one every other day to eight per day) in a single headache “cluster,” or course, may be lower up to half of the time.


Cluster headache often follows seasonal or time-of-day patterns. For this reason, researchers believe that cluster headache may be caused by abnormalities of the hypothalamus, which regulates our circadian cycles (or internal clock). Positron emission tomography (PET) scans have shown heightened activity in the hypothalamus during a cluster attack.


There are a number of known triggers for cluster headaches, and recognizing and avoiding them can help reduce the frequency of cluster episodes. Some triggers occur only during an attack period, and others will bring on a cluster episode after months of remission. For example, drinking alcohol during a remission period may not bother you at all, but having a drink during an active cluster period can cause a sudden cluster headache. And many people with cluster headaches have seasonal triggers for their cluster periods; for example, they may experience a cluster period every autumn.

Researchers have discovered a strong correlation between sleep patterns and cluster headache frequency and recurrence, so if you suffer from cluster headaches it's important to stay on a regular, fixed sleep schedule. Variances, such as an afternoon nap or a late night of studying, can trigger an attack.

Other known cluster headache triggers include:

  • Smoking and alcohol

  • Nitroglycerin used to treat heart conditions

  • Exposure to solvents and gasoline

  • Hypoxia (insufficient oxygen) due to sleep apnea or high altitude


One of the most effective and safest treatments for cluster headache pain is oxygen therapy. Inhaling 100 percent oxygen delivered at seven liters per minute through a mask can usually provide relief within five to fifteen minutes, with no side effects. However, because of the equipment involved, some patients may find oxygen therapy impractical. And while it is effective in about 90 percent of cluster headache patients, it doesn't work for everyone. And in some cases, head pain returns after the oxygen is discontinued.

Because the head pain of cluster headaches comes on severely and quickly, most over-the-counter analgesics aren't very effective. Medication for cluster headache is often administered via nasal spray or injection for rapid absorption.

Drug therapies for acute cluster headache pain include:

Abortive medications:

  • Sumatriptan (Imitrex): An effective drug delivered via nasal spray or subcutaneous injection. It's not recommended for people with certain heart problems.

  • Zolmatriptan (Zomig): A triptan drug available in oral and nasal spray form. Side effects may include dry mouth, dizziness, sweating, and weakness. Zomig should also be avoided in patients with heart conditions.

  • Ergotamine: Available in injectable, inhaler, and sublingual form. Nausea may be a problem with the use of these medications, which can also be dangerous if used more frequently than prescribed.

  • Intranasal lidocaine: This topical pain reliever is delivered in nasal drops or spray. It can decrease pain within five minutes and abort a headache within 35 minutes but is not consistently effective.

  • Intranasal capsaicin: Also applied to the inside of the nasal cavity, capsaicin has been shown to reduce headache severity after a week of treatment.

Prophylactic, or preventative, therapies are used for chronic or episodic cluster headache. These include:

Prophylactic medications:

  • Verapamil: An oral drug usually taken three times daily or once daily in a sustained-release preparation that can reduce the frequency of cluster attacks. A common side effect is constipation.

  • Prednisone: An oral steroid usually prescribed along with another prophylactic. Prednisone works quickly to prevent cluster headache, but because the adverse side effects of the drug start to increase with the length of time it is taken, prednisone is usually used temporarily while another prophylactic medication works its way up to therapeutic levels.

  • Ergotamine derivatives: A fast-acting drug available in a tablet that dissolves under the tongue and is taken 30 to 60 minutes before an anticipated attack. Ergotamine derivatives can be particularly helpful for patients who experience cluster attacks during sleep. These drugs cannot be used in conjunction with triptans.

  • Lithium: Effective in cluster prevention, but patients can become resistant to the drug over time. Long-term use and excessive dosing can produce tremor and can cause damage to the kidneys and thyroid, so frequent blood tests are required.

  • Valproic acid (Depakote): Usually helps prevent attacks within four days after starting treatment. Frequent blood and liver function tests are required for patients taking this therapy.

In patients not responsive to oxygen or drug therapy, an anesthetic nerve block injected into the occipital nerve may be attempted for pain relief. Surgical options involving manipulation or destruction of a portion of the facial nerves are also available, but due to the high risk of permanent nerve damage, these are a last-resort treatment.

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