The exact cause of migraine headaches is unclear, but research scientists agree that a key element is blood flow changes in the brain. Other possible causes could include an imbalance of brain chemicals or perhaps even genetics. Although the cause of this type of headache is unknown, migraines are often a result of controllable and uncontrollable migraine triggers.
What Causes Migraine Headaches?Migraine 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.
Other possible migraine causes may include:
- Imbalance of brain chemicals
Also, although the direct cause is unknown, this type of headache is often a result of controllable and uncontrollable migraine triggers (see Migraine Triggers for a list of specific triggers of migraine headaches).
Blood Flow TheoryOne possible cause of migraines is thought to be related to blood vessels. People who get migraine headaches appear to have blood vessels that overreact to various triggers.
Scientists have devised one theory about migraines that explains these blood flow changes, as well as 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 closes down or 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 a chemical called 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. Symptoms signaling a headache (such as distorted vision or speech) may then result -- similar to symptoms of a stroke (see Stroke Symptoms).
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, is a throbbing pain in the head.