Migraine Headaches Support Group

Migraine is a neurological disease, of which the most common symptom is an intense and disabling episodic headache. Migraine headaches are usually characterized by severe pain on one or both sides of the head and are often accompanied by photophobia (hypersensitivity to light), phonophobia (hypersensitivity to sound) and nausea. The word migraine is French in origin and comes from the Greek hemicrania (as does the Old English term megrim). Literally, hemicrania means "only half the head."

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

Scientists have devised one theory of migraine which explains these blood flow changes and also certain biochemical changes that may 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 artery and the carotid or neck arteries.

As these arteries constrict, the flow of blood to the brain is reduced. At the same time, blood-clotting particles called platelets clump together—a process which is believed to release the neurotransmitter serotonin. Serotonin acts as a powerful constrictor of arteries, further reducing the blood supply to the brain.

Reduced blood flow decreases the brain's supply of oxygen. Neurological symptoms signaling a headache, such as distorted vision or speech, may then result, similar to symptoms of stroke.

Reacting to the reduced oxygen supply, certain arteries within the brain open wider to meet the brain's energy needs. This widening or dilation spreads, finally affecting the neck and scalp arteries. The dilation of these arteries triggers the release of pain-producing substances called prostaglandins from various tissues and blood cells. Chemicals which cause inflammation and swelling, and substances which 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: a throbbing pain in the head.

More recent neuroimaging techniques seem to show that migraine is primarily a disorder of the brain (neurological), not of the blood vessels (vascular). A spreading depolarization (electrical change) may begin 24 hours before the attack, with onset of the headache occurring at about the time of maximum brain coverage. The effects of migraine may persist for some days after the main headache has ended. Many sufferers report a sore feeling in the area where the migraine was, and some report impaired thinking for a few days after the headache has passed.

In 2005, research was published indicating that in some people with a patent foramen ovale (PFO), a hole between the upper chambers of the heart, migraine might result and that the occurrence of migraines might end if the hole were blocked. Several clinical trials are currently under way in an effort to determine if a causal link between PFO and migraine can be found. Early speculation as to this relationship has centered on the idea that the lungs detoxify blood as it passes through. The PFO allows blood to go directly from the right side of the heart to the left without passing through the lungs.

Migraine is irregularly episodic, so there needs to be some explanation for why a particular migraine episode occurs at a particular time and not at another time. A migraine trigger is any factor that on exposure or withdrawal leads to the development of an acute migraine headache. Triggers may be categorized as behavioral, environmental, infectious, dietary, chemical, or hormonal. The trigger theory supposes that exposure to various environmental factors precipitates, or triggers, individual migraine episodes. Many people report that one or more dietary, physical, hormonal, emotional, or environmental factors precipitate their migraines. The most-often reported triggers include stress, over-illumination or glare, alcohol, foods, too much or too little sleep, and weather. Sometimes the migraine occurs with no apparent “cause.”

Migraine patients have long been advised to try to identify personal headache triggers by looking for associations between their headaches and various suspected trigger factors. Patients are urged to keep a “headache diary” in which to note what they eat and when they get a headache, to look for correlations, and to try to avoid headache by avoiding factors they identify as triggers. Typically this advice is accompanied by a list of trigger factors.