Migraine Headache

Migraine is a primary headache disorder characterized by recurrent headaches that are moderate to severe. Typically, the headaches affect one half of the head, are pulsating in nature, and last from two to 72 hours. Associated symptoms may include nausea, vomiting, and sensitivity to light, sound, or smell. The pain is generally made worse by physical activity. Up to one-third of people have an aura: typically a short period of visual disturbance which signals that the headache will soon occur. Occasionally, an aura can occur with little or no headache following it.

Migraines are believed to be due to a mixture of environmental and genetic factors. About two-thirds of cases run in families. Changing hormone levels may also play a role, as migraines affect slightly more boys than girls before puberty and two to three times more women than men. The risk of migraines usually decreases during pregnancy. The underlying mechanisms are not fully known. It is, however, believed to involve the nerves and blood vessels of the brain.

Although much about the cause of migraines isn't understood, genetics and environmental factors appear to play a role.
Migraines may be caused by changes in the brainstem and its interactions with the trigeminal nerve, a major pain pathway.
Imbalances in brain chemicals — including serotonin, which helps regulate pain in your nervous system — also may be involved. Researchers continue to study the role of serotonin in migraines.
Serotonin levels drop during migraine attacks. This may cause your trigeminal system to release substances called neuropeptides, which travel to your brain's outer covering (meninges). The result is headache pain.

Migraine headache triggers

Whatever the exact mechanism of the headaches, a number of things may trigger them. Common migraine triggers include:

• Hormonal changes in women. Fluctuations in estrogen seem to trigger headaches in many women with known migraines. Women with a history of migraines often report headaches immediately before or during their periods, when they have a major drop in estrogen.
  
  Others have an increased tendency to develop migraines during pregnancy or menopause.
  
  Hormonal medications, such as oral contraceptives and hormone replacement therapy, also may worsen migraines. Some women, however, may find their migraines occur less often when taking these medications.
• Foods. Aged cheeses, salty foods and processed foods may trigger migraines. Skipping meals or fasting also can trigger attacks.
• Food additives. The sweetener aspartame and the preservative monosodium glutamate, found in many foods, may trigger migraines.
• Drinks. Alcohol, especially wine, and highly caffeinated beverages may trigger migraines.
• Stress. Stress at work or home can cause migraines.
• Sensory stimuli. Bright lights and sun glare can induce migraines, as can loud sounds. Unusual smells — including perfume, paint thinner, secondhand smoke and others — can trigger migraines in some people.
• Changes in wake-sleep pattern. Missing sleep or getting too much sleep may trigger migraines in some people, as can jet lag.
• Physical factors. Intense physical exertion, including sexual activity, may provoke migraines.
• Changes in the environment. A change of weather or barometric pressure can prompt a migraine.
• Medications. Oral contraceptives and vasodilators, such as nitroglycerin, can aggravate migraines.

Source:  mayoclinic.org