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Overview
A migraine headache
is a form of vascular headache. Migraine headache is caused by a combination of
vasodilatation (enlargement of blood vessels) and the release of chemicals from
nerve fibers that coil around the blood vessels. During a migraine attack, the
temporal artery enlarges. (The temporal artery is an artery that lies on the outside
of the skull just under the skin of the temple.) Enlargement
of the temporal artery stretches the nerves that coil around the artery and cause
the nerves to release chemicals. The chemicals cause inflammation, pain, and further
enlargement of the artery. The increasing enlargement of the artery magnifies
the pain. Migraine attacks commonly
activate the sympathetic nervous system in the body. The sympathetic nervous system
is often thought of as the part of the nervous system that controls primitive
responses to stress and pain, the so-called "fight or flight" response.
The increased sympathetic nervous
activity in the intestine causes nausea, vomiting, and diarrhea. Sympathetic activity
also delays emptying of the stomach into the small intestine and thereby prevents
oral medications from entering the intestine and being absorbed. The impaired
absorption of oral medications is a common reason for the ineffectiveness of medications
taken to treat migraine headaches. The
increased sympathetic activity also decreases the circulation of blood, and this
leads to pallor of the skin as well as cold hands and feet. The increased sympathetic
activity also contributes to the sensitivity to light and sound sensitivity as
well as blurred vision.
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