Anatomy of a Migraine

Nobody is completely sure of what causes some people to have migraines and some not to. Doctors do know that they run in families. If one of your parents has migraine problems, you have a 50 percent chance of developing them. If both of your parents have migraines, you chances jump to about 70 percent.

A brain is struck by lightning to depict migraine pain
© iStockphoto/Don Bayley
Genetics play a major role in your chance of developing migraines.

Likewise, doctors don't know for sure what happens when a trigger causes a migraine, or what exactly happens in the brain. Right now they think that migraine is caused by a progression of several things:

  1. You encounter a trigger: Let's say you forgot to eat breakfast and lunch was late.
  2. Pain-sensing cells in your brain stem (nociceptors) pick up on this change in your routine and release a chemical (neuropeptides).
  3. This chemical attacks other pain-sensing cells nearby, making them more sensitive to pain. They also release neuropeptides.
  4. Some of these chemicals begin to work on the muscles surrounding the blood vessels near the surface of your brain. Those muscles relax, making the blood vessels dilate and causing more blood to flow. This is where doctors think the aura in a classic migraine comes from.
  5. Some of the neuropeptide chemicals cause the cranial (skull) vessels to begin leaking, making the tissue around the area swell.

Doctors now think that the combination of these factors -- increased sensitivity, swelling brain tissues and swelling of blood vessels -- is the cause of migraines.

Is a migraine just a really bad headache?
The short answer -- nope. A common headache is caused by the cranial blood vessels narrowing (vasoconstriction), while migraine pain is due to the expansion of those blood vessels (vasodilation). During a migraine, the tissue surrounding the brain is swollen, causing intense pain. Medication prescribed for a headache (developed to dilate the blood vessels), will actually increase migraine pain. This is just one of the many reasons why proper diagnosis of migraine is so important [source: M.A.G.N.U.M. - The National Migraine Association].