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What causes migraine headaches?

No one fully understands the exact cause(s) of migraine headaches. Many experts think that a migraine begins with abnormal brainstem (a part of the brain) activity that leads to spasm (rapid contraction) of blood vessels in the cerebrum (main part of the brain) and dura (the covering of the brain). The first wave of spasm decreases blood supply, which causes the aura that some people experience. After the first spasm, the same arteries become abnormally relaxed, which increases blood flow and gives rise to migraine headache pain.

Certain chemicals normally found in the brain (namely, dopamine and serotonin) may be involved in causing migraines. These chemicals are called neurotransmitters because they transmit signals within the brain. Neurotransmitters can cause blood vessels to act in unusual ways if they are present in abnormal amounts or if the blood vessels are particularly sensitive to them.

Various triggers are thought to bring about migraine in people who have a natural tendency for having migraine headaches. Different people may have different triggers.

• Certain foods, especially chocolate, cheese, nuts, alcohol, and monosodium glutamate (MSG) can trigger migraines. (MSG is a food enhancer used in many foods, including Chinese food.)
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• Missing a meal may bring on a headache.
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• Stress and tension are also risk factors. People often have migraines during times of increased emotional or physical stress.
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• Birth control pills are a common trigger. Women may have migraines at the end of the pill cycle as the estrogen component of the pill is stopped. This is called an estrogen-withdrawal headache.