Excerpt from Headache, Migraine

Synonyms, Key Words, and Related Terms: migraine variant, classic migraine, cluster headache, aura, dizziness, tinnitus, scotomas, photophobia, visual scintillations, bright zigzag lines, migraine with aura, migraine without aura, dopamine receptor hypersensitivity, visual aura, fortification spectra, geometric visual patterns, hemianopsia, blind spots, hallucinations, hemicrania, throbbing headache, pulsatile headache, lightheadedness, phonophobia, Valsalva maneuvers, hemiplegic migraine, aphasia, third nerve palsy, ophthalmoplegic migraine, ocular muscle paralysis, ptosis, alcohol consumption, fatigue, emotional stress, birth control pills, vasodilators

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Background: Migraine headaches are recurrent headaches that may be unilateral or bilateral. Migraine headaches may occur with or without a prodrome. The aura of a migraine may consist of neurologic symptoms, such as dizziness, tinnitus, scotomas, photophobia, or visual scintillations (eg, bright zigzag lines). In 1988, the International Headache Society (IHS) redefined and classified headaches to formulate the current categorization. The headache previously described as classic migraine is now known as migraine with aura, and that described as common migraine is now termed migraine without aura. Migraines without aura are the most common, accounting for more than 80% of all migraines.

In April 2000, the US Headache Consortium, a multispecialty group that includes the American College of Emergency Physicians, released evidence-based guidelines for the diagnosis, treatment, and prevention of migraine headaches. Guidelines are also available from the American Academy of Neurology, the National Headache Foundation, and the Canadian Association of Emergency Physicians.

Pathophysiology: The pathophysiology of migraine headaches is not clearly understood. Growing evidence supports the role of neurogenic peptides, such as serotonin and dopamine, in the brain. These vasoactive neuropeptides stimulate an inflammatory cascade with the release of endothelial cells, mast cells, and platelets. This inflammation causes vasodilation and a perivascular reaction. The serotonin receptor (5-HT) is believed to be the most important receptor in the headache pathway.

Some of the symptoms associated with migraine headaches, such as nausea (80%), vomiting (50%), yawning, irritability, hypotension, and hyperactivity, can be associated with dopamine receptor activation. Dopamine receptor hypersensitivity has been shown experimentally with dopamine agonists such as apomorphine, bromocriptine, and pergolide. Dopamine antagonists, such as metoclopramide (Reglan), haloperidol (Haldol), and prochlorperazine (Compazine), have been shown clinically to treat migraine headaches effectively.

Frequency:

In the US: An estimated 10-20% of the US population suffers from migraine headaches. Frequency of headaches varies greatly by individual. An estimated 6% of men and 15-17% of women in the United States have migraine. Migraine is the second most common type of headache syndrome in the United States. Tension headaches are the most common.

Sex: Migraines most commonly are found in women, with a 3:1 female-to-male ratio. In childhood, however, migraines are more common in boys than in girls.

Age: The first attack often is in childhood, and incidence increases in adolescence. More than 80% of patients who develop migraines will have a first attack by age 30. Migraines continue through the patient's 30s and 40s. They may begin or occur at any age but are rare after age 50. With increased age, attacks usually decrease in severity and frequency. Age older than 55 years is a strong predictor for intracranial pathology.