Migraine headaches are a type of neurovascular headaches, a category that also includes cluster headaches. Doctors believe that neurovascular headaches are caused by an interaction between blood vessel and nerve abnormalities. Migraine headaches are the second most common type of primary headache after tension headaches. A primary headache is a headache that is not caused by another disease or condition. [For more information, see In-Depth Report #11: Headaches – tension and Report #99: Headaches - cluster.]
Migraine headaches are characterized by throbbing disabling pain on one side of the head, which sometimes spreads to affect the entire head. In fact, migraine comes from the Greek word hemikrania, meaning “half of the head”.
Migraines are classified as occurring either:
- With aura (previously called classic migraine) or
- Without aura (previously called common migraine).
Auras are sensory disturbances that occur before a migraine attack that can cause changes in vision, with or without other neurologic symptoms. [For more information on auras, see Symptoms section of this report.]
Episodic and Chronic Migraine
Migraines typically occur as isolated episodic attacks, which can happen once a year or several times within one week. In some cases, patients eventually experience on-going and chronic migraine (previously called transformed migraine). Chronic migraines typically begin as episodic headaches when patients are in their teens or 20s, and then increase in frequency over time. A headache is considered chronic when it occurs at least half of the days in a month, and often on a daily or near-daily basis.
The majority of chronic migraines are caused by overuse of analgesic migraine medications, both prescription pain reliever drugs and over-the-counter medications. Medication overuse headaches are also called rebound headaches. Obesity and caffeine overuse are other factors that may increase the risk of episodic migraine transforming to chronic migraine.
Review Date: 11/04/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.