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What causes migraine headaches?

The typical migraine headache is unilateral (affecting one half of the head) and pulsating, lasting from 4 to 72 hours; symptoms include nausea, vomiting, photophobia (increased sensitivity to light), and phonopia (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 unknown; the most common theory is a disorder of the serotonergic control system.

The signs and symptoms of migraine vary among patients. Therefore, what a patient experiences before, during and after an attack cannot be defined exactly. The four phases of a migraine attack listed below are common but not necessarily experienced by all migraine sufferers. Additionally, the phases experienced and the symptoms experienced during them can vary from one migraine attack to another in the same migraineur:

1. The prodrome, which occurs hours or days before the headache.
2. The aura, which immediately precedes the headache.
3. The pain phase, also known as headache phase.
4. The postdrome.

Prodrome phase

Prodromal symptoms occur in 40–60% of migraineurs (migraine sufferers). This phase may consist of altered mood, irritability, depression or euphoria, fatigue, yawning, excessive sleepiness, craving for certain food (e.g. chocolate), stiff muscles (especially in the neck), constipation or diarrhea, increased urination, and other visceral symptoms. These symptoms usually precede the headache phase of the migraine attack by several hours or days, and experience teaches the patient or observant family how to detect that a migraine attack is near.

Aura phase

For the 20-30% of migraine sufferers who experience migraine with aura, this aura comprises focal neurological phenomena that precede or accompany the attack. They appear gradually over 5 to 20 minutes and generally last fewer than 60 minutes. The headache phase of the migraine attack usually begins within 60 minutes of the end of the aura phase, but it is sometimes delayed up to several hours, and it can be missing entirely. Symptoms of migraine aura can be visual, sensory, or motor in nature^.

Visual aura is the most common of the neurological events. There is a disturbance of vision consisting usually of unformed flashes of white and/or black or rarely of multicolored lights (photosia) or formations of dazzling zig zag lines (scintillating scotoma; often arranged like the battlements of a castle, hence the alternative terms “fortification spectra” or “teichopsia”. Some patients complain of blurred or shimmering or cloudy vision, as though they were looking through thick or smoked glass, or in some cases tunnel vision and hemianopsia. The somatosensory aura of migraine consists of digitolingual or cheiro-oral paresthesias, a feeling of pins-and-needles experienced in the hand and arm as well as in the nose-mouth area on the same side. Paresthesia migrate up the arm and then extend to involve the face, lips and tongue.

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^.

Pain Phase

The typical migraine headache is unilateral, throbbing, and moderate to severe and can be aggravated by physical activity. Not all these features are necessary. The pain may be bilateral at the onset or start on one side and become generalized, and usually it alternates sides from one attack to the next. The onset is usually gradual. The pain peaks and then subsides and usually lasts 4 to 72 hours in adults and 1 to 48 hours in children. The frequency of attacks is extremely variable, from a few in a lifetime to several a week, and the average migraineur experiences one to three headaches a month. The head pain varies greatly in intensity.

The pain of migraine is invariably accompanied by other features. Nuasea occurs in almost 90 percent of patients, and vomiting occurs in about one third of patients. Many patients experience sensory hyperexcitability manifested by photophobia, phonophobia, and osmophobia and seek a dark and quiet room. Blurred vision, nasal stuffiness, diarrhea, polyuria, pallor or sweating may be noted during the headache phase. There may be localized edema of the scalp or face, scalp tenderness, prominence of a vein or artery in the temple, or stiffness and tenderness of the neck. Impairment of concentration and mood are common. The extremities tend to feel cold and moist. Vertigo may be experienced; a variation of the typical migraine, called vestibular migraine, has also been described. Lightheadedness, rather than true vertigo, and a feeling of faintness may occur.

Postdrome phase

The patient may feel tired or “hungover” and have head pain, cognitive difficulties, gastrointestinal symptoms, mood changes, and weakness. Some people feel unusually refreshed or euphoric after an attack, whereas others note depression and malaise. Often, some of the minor headache phase symptoms may continue, such as loss of appetite, photophobia, and lightheadedness. For some patients, a 5- to 6-hour nap may reduce the pain, but slight headaches may still occur when the patient stands or sits quickly. These symptoms may go away after a good night’s rest, although there is no guarantee. Some people may suffer and recover differently than others.