Migraine Headache Health Article

Etiology

Researchers are unclear about the precise cause of migraine headaches. There seems to be general agreement that a key element is blood flow changes in the brain. Persons who get migraine headaches appear to have blood vessels that overreact to various triggers.

Scientists have devised one theory of migraine that explains these blood flow changes and also certain biochemical changes that might be involved in the headache process. According to this theory, the nervous system responds to a trigger such as stress by causing a spasm of the nerve-rich arteries at the base of the brain. The spasm constricts several arteries supplying blood to the brain, including the scalp and the carotid arteries.

As these arteries constrict, the flow of blood to the brain is reduced. At the same time, platelets clump together; this process is believed to release serotonin. Serotonin acts as a powerful constrictor of arteries, thus further reducing the blood supply to the brain.

Reduced blood flow decreases the brain's supply of oxygen. Symptoms signaling a headache, such as distorted vision or speech, can result.

Reacting to the reduced oxygen supply, certain arteries within the brain dilate to meet the brain's energy needs. This dilation spreads, finally affecting the neck and scalp arteries. The dilation of these arteries triggers the release of prostaglandins from various tissues and blood cells. Chemicals that cause inflammation and swelling and substances that increase sensitivity to pain are also released. The circulation of these chemicals and the dilation of the scalp arteries stimulate the pain-sensitive nociceptors. The result, according to this theory, is a throbbing pain in the head.

The relationship between female hormones and migraine is still unclear. Women can have "menstrual migraine"'headaches around the time of their menstrual period'that disappears during pregnancy. Other women develop migraine for the first time when they are pregnant, and some are first affected after menopause.

The effect of oral contraceptives on headaches remains perplexing. Scientists report that some women with migraine who take birth control pills experience more frequent and severe attacks. However, a small percentage of women have fewer and less-severe migraine headaches when they take birth control pills. In addition, women who do not have headaches can develop migraines as a side effect when they use oral contraceptives.

Many persons who have migraine headaches have a positive family history. The exact hereditary nature of this condition is still unknown, although affected persons are thought to have an inherited abnormality in the regulation of blood vessels.

The onset of migraine headaches is often triggered by certain events or conditions. These triggers include stress and other normal emotions as well as biologic and environmental conditions. Fatigue, glaring or flickering lights, changes in the weather, lack of sleep, hormonal irregularities (in women only), anxiety, stress, and certain foods can set off migraine.

Some scientists believe that certain foods (eg, yogurt, nuts, lima beans) contain chemical substances such as tyramine. These substances constrict arteries and initiate the migraine process. Other scientists believe that foods cause headaches by setting off an allergic reaction in susceptible persons.

Although a food-triggered migraine usually occurs soon after eating, other triggers might not cause immediate pain. Scientists report that persons can develop migraine not only during a period of stress but also afterward, when their vascular systems are still reacting.

Symptoms

Symptoms of migraine can vary, and certain symptoms are associated with different types of migraines.

A classic migraine headache is often accompanied by extreme sensitivity to light and sound, nausea, and vomiting. Some persons can predict the onset of a classic migraine, because it is preceded by an "aura", which is a visual disturbance that appears as flashing lights, zigzag lines, or a temporary loss of vision.

A common migraine is not preceded by an aura. However, some persons experience a variety of vague symptoms beforehand, including mental fuzziness, mood changes, fatigue, and unusual retention of fluids. During the headache phase of a common migraine, a person can have diarrhea and increased urination as well as nausea and vomiting.

In addition to temporary paralysis, some persons with hemiplegic migraine can experience vision problems and vertigo. These symptoms begin 10 to 90 minutes before the onset of headache pain.

Symptoms in patients with ophthalmoplegic migraine can include a droopy eyelid, diplopia, and other visual problems.

Persons having basilar artery migraines often have preheadache symptoms that can include vertigo, diplopia, and poor muscular coordination.

Finally, patients who have headache-free migraines can have visual problems, nausea, vomiting, constipation, or diarrhea.