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Migraine: Overview and Risk Factors

Migraine is a recurrent condition marked by severe episodic headaches, other neurologic manifestations, or both. Migraine may be caused by dysfunction of the trigeminovascular system and is attended by a wave of hyperpolarization of cells and hypoperfusion across the cerebral cortex. These events can cause the patient to experience an “aura,” a state characterized by unusual visual or other sensory phenomena. The headache is believed to result from multiple factors, including sensitization of trigeminal sensory neurons and activation of the trigeminovascular system, altered serotonin metabolism, the release of vasoactive polypeptides such as substance P, causing inflammation of the meninges.1–3

In approximately 60% of cases, the headache is unilateral, but it can occur globally and bifrontally, as well as (rarely) in other patterns. Pain escalation is gradual, progressing from dull to throbbing in most cases, and can be exacerbated by light, sound, and activity. Explosive onsets of headaches should be investigated for alternative causes, although this pattern, too, may represent migraine.

Migraines typically begin in the teenage years or early adulthood; they rarely commence after age 40. There are uncommon variants of migraine including retinal, ophthalmoplegic, and familial hemiplegic. Migraine without aura (“common” migraine) makes up about 80% of all cases. Migraine with aura (“classic” migraine) is the second most common type.

Aura is caused by neuronal dysfunction. The most common manifestations are visual phenomena (flashing lights, jagged lines, and scotomata, usually still visible with the eyes closed), with other sensory symptoms (altered taste or smell, tingling or numbness, dizziness). Migraines with motor symptoms are classified as familial or sporadic hemiplegic migraine. Auras typically last no more than an hour, except in cases of motor dysfunction. In complicated migraines, neurologic symptoms may last weeks or may be permanent (usually with evidence of a stroke). Aura without headache (acephalgic migraine or “atypical migraine”) may also occur.

Symptoms that suggest that a headache may be migraine include:

  • Multiple headaches of moderate–to–severe intensity, lasting from hours to days
  • Unilateral, throbbing quality
  • Photophobia, phonophobia
  • Nausea/vomiting
  • Aggravation of headache by activity
  • Autonomic features such as rhinorrhea or congestion, tearing, changes in pupil size, and others (these occur occasionally, not routinely)4
  • Pain sensation with normal stimuli (cutaneous allodynia)

Triggers include stress, menses, oral contraception, overexertion, sleep deprivation, fasting, head trauma, bright lights, changes in weather, changes in eating or sleeping schedules, and substances in food or beverages, such as nitrites, glutamate, aspartate, and tyramine. Other identified triggers are excessive vitamin A intake, histamine, corticosteroid withdrawal, caffeine or analgesic withdrawal, and strong odors.5 Triggers may act as vasodilators2,6 or through allergic reactions.7,8

Risk Factors

Up to 60% of migraine cases are familial, with specific gene abnormalities in some cases. Women are affected about 3 times more often than men.9 Persons with right–to–left cardiac shunts (patent foramen ovale, and atrial septal defect to a lesser degree) have increased migraine prevalence,10–12 for unknown reason.


Migraine: Diagnosis and Treatment >>