Headaches: Cluster - Causes

Highlights	Risk Factors	Surgery
Introduction	Diagnosis	Resources
Cluster Headaches	Managing Cluster Headaches	References
Causes	Treatment
Prognosis	Medications

Causes

Cluster headaches, like migraines, are likely due to an interaction of abnormalities in the blood vessels and nerves that affect regions in the face.

Abnormalities in the Hypothalamus

Evidence now strongly suggests that abnormalities in the hypothalamus, a complex structure located deep in the brain, may play a major role in cluster headaches. Advanced imaging techniques have revealed that a specific area in the hypothalamus is asymmetrical in these patients and is activated during a cluster headache attack.

The hypothalamus is involved in the regulation of many important chemicals and nerve pathways, including the following:

Nerve clusters that regulate the body's biologic rhythms (its circadian rhythms).

Click the icon to see an image of the hypothalamus.

Serotonin and norepinephrine. These are neurotransmitters (chemical messengers in the brain) that are involved with well being and appetite.
Cortisol (stress hormones).
Melatonin (a hormone related to the body's response to light and dark).
Beta-endorphins (substances that modulate pain).

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Circadian Abnormalities. Cluster attacks often occur during specific sleep stages. They also often follow the seasonal increase in warmth and light, beginning in summer and ending in the fall. Researchers have therefore focused attention on circadian rhythms, and in particular small clusters of nerves in the hypothalamus that act like biologic clocks.

The most important nervous cluster is the suprachiasmatic nuclei (SCN), which appears to help coordinate the body's activities (sleep/wake) with the environment (dark/light). Some studies support the idea that some failure in this biologic pacemaker may impair the pain control system and cause these terrible attacks.

The hormone melatonin is also involved in the body's biologic rhythms.

Alterations in Serotonin. The brain chemical serotonin is of particular interest in the study of headaches, particularly migraine and cluster headaches. This neurotransmitter (chemical messenger) affects, among other functions, well being, sleep, and appetite. Some research has also suggested that serotonin may play an important role in the way circadian rhythms are expressed. There is some evidence of abnormal regulation of brain serotonin levels in cluster patients (although it is not as pronounced as in migraine patients).

Dilation of Blood Vessels

Cluster headaches are associated with dilation (widening) of blood vessels and inflammation of nerves behind the eye.

Cluster headaches may be caused by blood vessel dilation in the eye area. Inflammation of nearby nerves may give rise to the distinctive stabbing, throbbing pain usually felt in one eye. The trigeminal nerves branch off the brainstem behind the eyes and send impulses throughout the cranium and face.