Migraine is a neurological syndrome characterized by altered bodily perceptions, severe headaches, and nausea. Physiologically, the migraine headache is a neurological condition more common to women than to men. The word ''migraine'' was borrowed from Old French ''migraigne'' (originally as "megrim", but respelled in 1777 on a contemporary French model). The French term derived from a vulgar pronunciation of the Late Latin word ''hemicrania'', itself based on Greek ''hemikrania'', from Greek roots for "half" and "skull".
The typical migraine headache is unilateral and pulsating, lasting from 4 to 72 hours; symptoms include nausea, vomiting, photophobia (increased sensitivity to light), and phonophobia (increased sensitivity to sound); approximately one-third of people who suffer migraine headache perceive an aura—unusual visual, olfactory, or other sensory experiences that are a sign that the migraine will soon occur.
Initial treatment is with analgesics for the headache, an antiemetic for the nausea, and the avoidance of triggering conditions. The cause of migraine headache is idiopathic; the accepted theory is a disorder of the serotonergic control system, as PET scan has demonstrated the aura coincides with diffusion of cortical depression consequent to increased blood flow (up to 300% greater than baseline).
There are migraine headache variants, some originate in the brainstem (featuring intercellular transport dysfunction of calcium and potassium ions) and some are genetically disposed. Studies of twins indicate a 60 to 65 percent genetic influence upon their propensity to develop migraine headache. Moreover, fluctuating hormone levels indicate a migraine relation: 75 percent of adult patients are women, although migraine affects approximately equal numbers of prepubescent boys and girls; propensity to migraine headache is known to disappear during pregnancy, although in some women migraines may become more frequent during pregnancy.
The International Headache Society (IHS) classifies migraine headache.
Defining pain severity
The IHS defines the intensity of pain with a verbal, four-point scale:
|0||no pain|| |
|1||mild pain||does not interfere with usual activities|
|2||moderate pain||inhibits, but does not wholly prevent usual activities|
|3||severe pain||prevents all activities|
Migraine is an extremely common condition which will affect 12–28% of people at some point in their lives. However this figure — the lifetime prevalence — does not provide a very clear picture of how many patients there are with active migraine at any one time. Typically, therefore, the burden of migraine in a population is assessed by looking at the one-year prevalence — a figure that defines the number of patients who have had one or more attacks in the previous year. The third figure, which helps to clarify the picture, is the incidence — this relates to the number of first attacks occurring at any given age and helps understanding of how the disease grows and shrinks over time.
Based on the results of a number of studies, one year prevalence of migraine ranges from 6–15% in adult men and from 14–35% in adult women. There is then a rapid growth in incidence amongst girls occurring after puberty, which continues throughout early adult life. By early middle age, around 25% of women experience a migraine at least once a year, compared with fewer than 10% of men. After menopause, attacks in women tend to decline dramatically, so that in the over 70s there are approximately equal numbers of male and female sufferers, with prevalence returning to around 5%. Incidence figures show that the excess of migraine seen in women of reproductive age is mainly due to migraine without aura.
There is a strong relationship between age, gender and type of migraine.
Geographical differences in migraine prevalence are not marked. Studies in Asia and South America suggest that the rates there are relatively low, but they do not fall outside the range of values seen in European and North American studies.
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