Migraines are paroxysmal, usually unilateral, severe headache lasting 2-72 hours, accompanied by gastrointestinal, visual, or other neurological signs, and with complete freedom from symptoms between episodes. Episodes vary in frequency from weekly to less than one per year. Common migraines (without aura) affects 80% of patients, whereas the classic migraine (with aura - consistent warning symptoms before the headache) affects less than 20% of patients.
The exact cause of migraines is unknown. Several mechanisms have been proposed, including: Abnormality of serotonin metabolism; Disturbance of regional cerebral blood flow; and Dilatation of scalp arteries.
Individual attacks may be precipitated by: Specific foods (chocolate, cheese, smoked meats) or alcohol (red wine); Missing meals; Menstrual cycle or Oral contraceptives; Fatigue or excessive sleep; Excessive or flickering light; or Stress or relief of stress (the "weekend migraine").
Risk factors include: Family history of migraine; Female sex; Young age; and a Personal history of childhood recurrent abdominal pain, cyclical vomiting, or motion sickness.
Food additives can produce systemic symptoms (monosodium glutamate); asthma (metabisulfite, tartrazineÑa yellow dye); and possibly urticaria (tartrazine). Aspartame (Nutrasweet) in diet sodas can also cause headaches.
Migraines may also be caused by valvular heart disease (mitral valve prolapse) which causes orthostatic hypotension and excess sympathetic tone (catecholamine release).
Serotonin metabolism is the focus of recent research. The mechanism is related to episodic reductions in serotonin which causes intracranial arterial vasodilation. Prodromal symptoms may be due to intracerebral vasoconstriction, and some attribute the head pain to substances released by the dilation of scalp arteries.
Migraines have been associated with hormonal changes in women. A drop in estrogen levels may precipitate migraine attacks. Menopausal estrogen replacement can, however, both alleviate and contribute to migraine occurrence. Estrogen increases the production of serotonin in the body and also influences the way in which serotonin binds to nerve cells. It is possible, then, that low levels of estrogen, as are seen at the time of menstruation, could cause changes in the serotonin system, followed by headache.
Standard lab tests are used to rule out other causes of headaches. A SED rate will be elevated in temporal arteritis. A complete blood count is ordered if meningitis or encephalitis is suspected. Imaging studies may be ordered to rule out cerebral tumor or vascular malformation.
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