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 hormone melatonin is also involved in the body's biologic rhythms.
Dilation of Blood Vessels
Cluster headaches are associated with dilation (widening) of blood vessels and inflammation of nerves behind the eye.
What causes these events and how they relate to cluster headaches are still unclear. Because blood vessel dilation appears to follow, not precede, the pain, some action originating in the brain is likely to be part of the primary process.
Abnormalities in the Sympathetic Nervous System
Some evidence suggests that abnormalities in the sympathetic (also called autonomic) nervous system may contribute to cluster headaches. This system regulates non-voluntary muscle actions in the body, such as in the heart and blood vessels.
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Review Date: 09/29/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
