sometimes the textbooks classify the difference between a migraine an aura. It is most often one sided and is thought to be created by a vascular spasm in the brain. You usually have an aversion to light and sound and usually nausea.

hope this helps
http://zomig.com/what/migraine.aspx?ce=set

http://www.mayoclinic.com/health/mig...120/DSECTION=3

hugs,
Victoria