What are cluster headaches?

Cluster headaches are the most severe headaches. A cluster headache can be many times more intense than a migraine attack. It has been called the "suicide headache" because some people have taken their lives either during an attack or in anticipation of an attack.

The term "cluster headache" refers to headaches that have a characteristic grouping of attacks. Cluster headaches occur up to eight times per day during a cluster period, which may last 2 weeks to 3 months, or longer. The headaches may disappear completely (go into "remission") for months or years, only to recur at a later date. A cluster headache typically awakens a person from sleep 1 to 2 hours after going to bed. These nocturnal attacks can be more severe than the daytime attacks.

Who is affected by cluster headaches?

Cluster headaches are an uncommon type of primary headaches (i.e., a headache that has no structural cause), affecting less than 1 in 1,000 people. Cluster headaches are a young person's disease, and the headaches typically start before age 30. Cluster headaches are more common in men, but more women are starting to be diagnosed with this disorder. The male-to-female gender headaches appear to be six times more common in men than women, especially men in their 20s or 30s.

What causes cluster headaches?

The true biochemical cause of cluster headaches is unknown. However, the headaches occur when a trigeminal-autonomic reflex pathway in the brainstem is activated. The trigeminal nerve is the chief sensory nerve of the face. When activated, the trigeminal nerve leads to the eye pain associated with cluster headaches. The trigeminal nerve also stimulates the parasympathetic autonomic system, which causes the eye tearing and redness, nasal congestion and discharge with cluster attacks. Cluster headaches appear to be generated by the hypothalamus (the part of the brain that is home to the suprachiasmatic nucleus or circadian clock). Recent imaging studies have shown activation or stimulation of the hypothalamus during a cluster attack.

Cluster headaches usually are not caused by an underlying condition such as a tumor or aneurysm. Thus, they are considered to be a form of ‘primary' headache.

What triggers cluster headaches?

The season is the most common trigger for cluster headaches, which often occur in the spring or autumn. Due to their seasonal nature, cluster headaches are often mistakenly associated with allergies or sinusitis. The seasonal nature of cluster headaches most likely results from stimulation or activation of the hypothalamus.

Cluster headaches are also common in people who smoke and drink alcohol frequently and a large proportion of the patients have sleep apnea.

During a cluster period, the sufferer is more sensitive to the action of alcohol and nicotine, and minimal amounts of alcohol can trigger the headaches. During headache-free periods, the patient can consume alcohol without provoking a headache.

Smoking can also increase the severity of cluster headaches during a cluster period.

What are the symptoms of a cluster headache?

Cluster headaches generally reach their full force within five or ten minutes after onset. The attacks are usually very similar, varying only slightly from one attack to another.

Type of pain

The pain of cluster headache is one-sided, and during a headache period, the pain remains on the same side. When a new headache period starts, it rarely occurs on the opposite side.

Severity/intensity of pain

The pain of cluster headache is generally very intense and severe and is often described as having a burning or piercing quality. It may be throbbing or constant. The pain is so intense that most cluster headache sufferers cannot sit still and will often pace during an attack.

Location of pain

The pain is located behind one eye or in the eye region, without changing sides. It may radiate to the forehead, temple, nose, cheek, or upper gum on the affected side.

The scalp may be tender, and the pulsing in the arteries often can be felt.

Duration of pain

The pain of a cluster headache can last anywhere from 15 minutes to three hours. In general, the headaches last for 30 to 90 minutes. The headache will disappear only to recur later that day. Typically, in between attacks, people with cluster headaches are headache free but the pain can sometimes linger.

Frequency of headaches

Most sufferers get one to three headaches per day during a cluster period (the time when the headache sufferer is experiencing daily attacks). They occur very regularly, generally at the same time each day, and they often awaken the person at the same time during the night.

The cluster periods can last from two weeks to three months and then disappear completely for months or years. The episodic cluster headache sufferer has variable pain-free intervals between headache attacks.

Attacks appear to be linked to the circadian (or "biological") clock. Most people with cluster headaches will develop cluster periods at the same time each year -- either in the spring or fall or the winter or summer.

Most cluster sufferers (80% to 90%) have episodic cluster headaches that occur in periods lasting seven days to one year, separated by pain-free episodes lasting 30 days or more.

In about 20% of people with cluster headaches, the attacks may be chronic. Some patients will note that the series of headaches are not separated by periods of remission lasting longer than a month. These cases are chronic.

What are the warning signs of a cluster headache?

Although the pain of a cluster headache starts suddenly, a minimal type of warning of the oncoming headache may occur, including a feeling of discomfort or a mild one-sided burning sensation.

What are some associated symptoms of a cluster headache?

The affected eye may become swollen or droop. The pupil of the eye may get smaller and the conjunctiva (the tissue that lines the inside of the eyelid) will redden. There may be nasal discharge or congestion and tearing of the eye during an attack, which occur on the same side as the pain.

Excessive sweating may occur, and the face may become flushed on the affected side. Cluster headaches are not typically associated with the nausea or vomiting. People with cluster headaches appear to develop as much sensitivity to light that are found in other types of headaches, such as migraine and sound as people who have migraines.

It is possible for someone with cluster headaches to also suffer from migraines.

People who suffer from cluster headaches--especially people who have tooth or cheek pain with the cluster attacks--have an increased risk of developing a stomach ulcer.

Researchers believe that histamines, which dilate or expand blood vessels, influence the onset of a cluster headache because during a cluster headache, the level of histamine increases in a person's blood and urine.

Last reviewed by a Cleveland Clinic medical professional on 07/22/2014.

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