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Introduction

The term "cluster headache" refers to a type of headache that recurs over a period of time. People who have cluster headaches experience an episode one to three times per day during a period of time (the cluster period), which may last from 2 weeks to 3 months. The headaches may disappear completely (go into "remission") for months or years, only to recur. 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. Attacks appear to be linked to the circadian rhythm (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.

Cluster headaches are one of the most severe types of headache. It can be 100 times more intense than a migraine attack.

Who Gets Cluster Headaches?

Cluster headaches are the least common type of headaches, affecting less than 1 in 1,000 people. Cluster headaches are a young person's disease: the headaches typically start before age 30. Cluster headaches are more common in men, but more women are starting to be diagnosed with this problem. The male to female ratio is 2-3:1.

What Causes Cluster Headaches?

The true biochemical cause of cluster headaches is unknown. However, the headaches occur when a nerve pathway in the base of the brain (the trigeminal-autonomic reflex pathway) is activated. The trigeminal nerve is the main nerve of the face responsible for sensations (such as heat or pain.)

When activated, the trigeminal nerve causes the eye pain associated with cluster headaches. The trigeminal nerve also stimulates another group of nerves that causes the eye tearing and redness, nasal congestion, and discharge associated with cluster attacks.

The activation of the trigeminal nerve appears to come from a deeper part of the brain called the hypothalamus. The hypothalamus is home to our "internal biologic clock" which regulates our sleep and wake cycles on a 24-hour schedule. Recent imaging studies have shown activation or stimulation of the hypothalamus during a cluster attack.

Cluster headaches are not caused by an underlying brain condition such as a tumor or aneurysm.