- Central nervous system disorder: The precise cause of a
migraine attack is not completely understood. There appears to be general
agreement, however, that a key element is changes in the blood flow within the
brain due to a variety of triggers. The most widely accepted theory suggests
that a migraine attack is precipitated when pain-sensing nerve cells in the
brain (called nociceptors) release chemicals called neuropeptides (nerve
proteins) in response to stimulation of the trigeminal nerve system. At least
one of the neurotransmitters (chemicals that transmit impulses to the brain),
substance P, increases the pain sensitivity of other nearby nociceptors. Other neuropeptides
act on the smooth muscle surrounding cranial (skull) blood vessels, causing
inflammation. This smooth muscle regulates blood flow in the brain by causing
vasodilation (relaxation of blood vessels) or vasoconstriction (contracting the
blood vessel). At the onset of a migraine headache, neuropeptides are thought
to cause muscle relaxation, allowing vessel dilation and increased blood flow.
Other neuropeptides increase the permeability of cranial (skull) blood vessels,
allowing fluid containing inflammatory chemicals to leak and promote
inflammation and tissue swelling. The pain of migraine is though to result from
this combination of increased pain sensitivity, tissue, and vessel swelling,
and inflammation.
- Heredity: Susceptibility to migraine may be inherited. A
child of a migraine sufferer has as much as a 50% chance of developing a
migraine attack in their lifetime. If both parents are affected, the chance
rises to 70%. However, the gene or genes responsible have not been identified.
Genetics also increase the chances of having migraine attacks that are chronic
(or long-term).
- Neurotransmitters: Neurotransmitters are chemical messengers
in the brain. Two important ones, serotonin and dopamine, appear to be critical
in the processes leading to a migraine attack. Serotonin (also called
5-hydroxytryptamine or 5-HT) is involved in regulation of pain perception and
mood, among other important functions. A number of studies have suggested that
serotonin can stop the migraine process. To support this observation,
higher-than-normal levels of a serotonin compound are excreted in urine and
levels of serotonin in the blood drop during a migraine attack. Also, drugs
that target receptors in the brain for serotonin are generally effective in
stopping a migraine. The receptors for serotonin implicated in a migraine
attack are found on the trigeminal nerve endings. Serotonin appears to block
the peptides (including substance P) involved in over-stimulating nerves and
producing inflammation.
- Dopamine, another important neurotransmitter, may act as a
stimulant or accelerator of the migraine process. Some evidence suggests that
certain genetic factors make people over-sensitive to the effects of dopamine,
which include nerve cell excitation. Such nerve-cell over-activity could
trigger the events in the brain leading to migraine. The prodromal symptoms
(including mood changes, yawning, or drowsiness), for example, have been
associated with increased dopamine activity. Dopamine receptors are also
involved in regulation of blood flow in the brain, which may be of importance
when dealing with vasoconstriction and vasodilation.
- Calcium-channels: Some migraines may be due to abnormalities
in the channels within cells that transport the electrical ions calcium,
magnesium, sodium, and potassium. Calcium-channels regulate the release of
serotonin, an important neurotransmitter in the migraine process. Magnesium
interacts with calcium-channels and magnesium deficiencies have been detected
in the brains of migraine patients. Calcium-channels also play a major role in
cortical spreading depression (CSD), a brain event that includes a
"wave" of nerve impulses (firing) that spreads across the surface of
the brain, moving from the back (occipital region) of the cerebral cortex toward
the front at about one-eighth to three-sixteenth inches (three to five
millimeters) per minute. After the nerve excitation, a depression in nerve cell
function occurs that can last for minutes. CSD is thought to be one of the
causes of a migraine attack. Some individuals with migraine may inherit one or
more factors that impair calcium-channels, making them susceptible to
headaches. For example, mutations in a gene that encodes calcium channels
appears to be responsible for familial hemiplegic migraine.
- Gender and Age: A migraine attack is three times more common
in women than in men. Although the exact relationship between hormones and
headaches is not clear, fluctuations in estrogen and progesterone seem to
trigger headaches in many women with migraine headaches, including those with
premenstrual syndrome (PMS) and menopause. It seems to be hormonal
fluctuations, or changes, that trigger migraine attacks, not the presence of
the hormone. Prepubescent females, or females prior to reproductive maturity, can
also suffer from migraines. Women with a history of migraines often have
reported headaches immediately before or during their periods. Others report
more migraines during pregnancy or menopause. Hormonal medications, such as
oral contraceptives (birth control pills) and hormone replacement therapy (HRT,
including estrogen and progesterone therapy), may also worsen migraines. In
children younger than 10 years, boys appear to have migraines more often than
girls. After puberty starts, migraine headaches are much more common in females
(female-to-male ratio, 3:1), most likely due to hormonal changes.
- In general, the rate of migraine occurrence in males drops
to a low by age 28-29 years, with one case per 1,000 people in this age group.
- Migraine occurrence among females increases sharply up to
age 40 years and then declines gradually.
- The age when migraine headache with aura begins appears to
peak at or before age 4-5 years (6.6 cases per 1000 people in that age group),
while the highest rate for migraine without aura occurs at age 10-11 years
(10.1 cases per 1000 people in that age group).
- The severity and frequency of attacks tend to lessen with
age. Data suggests that migraine attacks are a chronic (long-term) condition,
although long remissions (illness-free periods) are common. One study showed
that 62% of young adults were free of migraine headaches for more than two
years, but only 40% continued to be free of them after 30 years.
- Diet: Certain foods and beverages appear to trigger
headaches in sensitive individuals. Common dietary triggers include alcohol
(especially beer and red wine), aged cheeses, chocolate, fermented, pickled, or
marinated foods (tofu, kim chee, miso), aspartame (an artificial sweetener),
caffeine, monosodium glutamate (MSG, a key flavor enhancer in some Asian
foods), and many canned and processed foods. Skipping meals or fasting also can
trigger migraines. Eating proper food is very important in migraine prevention
because a continuous supply of proper nutrients is essential to keeping
chemical balance in the brain. Brain chemistry can be changed significantly by
a single meal and, in turn, some changes in food composition can rapidly affect
brain function. While all foods eaten modify brain function, some specifically
alter mood or energy, such as caffeine or refined sugars. Eating unhealthy
foods that do not supply adequate nutrients for proper brain function, or foods
that alter brain function can cause migraine attacks in susceptible individuals
- Magnesium deficiency: Because levels of magnesium (a mineral
involved in nerve cell function) also drop right before or during a migraine
headache, it is possible that low amounts of magnesium may cause nerve cells in
the brain to misfire. About 20% of the population consumes less than two-thirds
of the RDA (recommended dietary allowance) for magnesium.
- Stress: A period of hard work followed by relaxation may
lead to a weekend migraine headache. Acute (immediate) or chronic (long-term)
stress at work or home also can set off a migraine.
- Sensory stimulus: Bright lights, sun glare, and unusual
smells, including pleasant scents (such as perfume or flowers), and unpleasant
odors (such as paint thinner and secondhand smoke) can trigger a migraine
attack.
- Physical factors: Intense physical exertion, including
sexual activity, may provoke migraines. Changes in sleep patterns, including
too much or too little sleep, also can initiate a migraine headache. Sleep
changes are usually seen in both adults and children with migraines. Healthcare
professionals recommend eight hours of uninterrupted sleep nightly for adults.
Sleep helps regulate certain neurochemicals (brain chemicals), including
serotonin. Decreases in serotonin may cause a migraine attack.
- Environmental changes: A change of weather, season, altitude
level, barometric pressure, or time zone can prompt a migraine headache.
Environmental changes such as moving to a new area where the plants and pollens
are different may also trigger a migraine attack.
- Medications: Taking certain medications can aggravate
migraines, including oral contraceptives (birth control pills), estrogen
replacement therapy, nitrates (nitroglycerin), theophylline (Slobidぐ),
reserpine (Serpasilぐ), nifedipine (Procardiaぐ or Adalatぐ), indomethicin
(Indocinぐ), cimetidine (Tagametぐ), decongestant overuse (such as
pseudoephedrine or Sudafedぐ), and anti-anxiety drug withdrawal, including
alprazolam (Xanaxぐ) and diazepam (Valiumぐ). Caffeine withdrawal and the
discontinuation of pain medications can trigger a migraine.
Copyright か 2007 Natural Standard Inc.
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