A migraine is a severe vascular headache that is usually worse on the sides of the head but can also occur on only one side of the head.
Blood vessels in the head supply the scalp and brain with blood.
Migraine headaches occur when these blood vessels dilate and stretch, causing the vessels to widen and then narrow rapidly.
Pain fibers in the blood vessel walls become irritated and the nerves surrounding the blood vessels release chemicals, sending pain signals to the brain.
The cause of migraine headaches is unclear, but scientists theorize that blood flow changes and certain biochemical changes are involved.
Migraines are a common type of chronic headache. A classic migraine is preceded by an aura, which is a group of warning symptoms that indicates a pending migraine headache. A common migraine does not have an associated aura. Migraines commonly occur in women, which may be due to the hormonal changes associated with a woman’s menstrual cycle.
A health care provider should be seen if migraine symptoms are severe, persistent, recurrent or are accompanied by other symptoms. Preventive medications as well as avoiding "triggers" that have brought on a migraine in the past may reduce the number of migraine headaches.