Migraine and Headache Dictionary

Vasodilation

The decrease in diameter of the blood vessels. This is the normal way that blood vessels control blood flow. However, when they start to dilate or constrict for no good reason, they could be involved in causing migraine symptoms.

Changes in blood vessels were once believed to be a main cause of migraine. However, now researchers believe the problem has more to do with other chemical messages in the brain.

Read this article for more on the cause of migraine.