Nerve pathway changes and imbalances in brain chemistry may cause blood vessels to become inflamed. The actual interaction between the brain chemistry and blood vessel dilation is not clear, but scientists believe that migraines are caused by alterations in the nerve pathways - specifically it is the trigeminal nerve system that is a major pathway in the brain. The trigeminal nerve pathway carries nerve signals from the head and face to the brain. When a migraine is triggered, the trigeminal nerve releases neuropeptides causing inflammation and dilation of the blood vessels. Subsequently, trigeminal nerve endings stimulate the release of more neuropeptides and a vicious cycle is begun.
Serotonin regulates pain messages via the trigeminal pathway.
Three out of four migraineurs are women and migraine is considered a hereditary disease. Migraines are generally of two types, known as classic and common. Typically, migraines are biased to one side of the head and often the pain is localized. Common migraine is considered any migraine not preceded by an aura or other symptomatic warning to the patient. Migraines often start in the teen years but are more likely to occur for the first time between 20 and 40 years of age.