Hi Alix,
Typcially in Migraine disease (a genetic neurologic disorder) MRI's are normal and are unable to show where pain takes place. A PET scan may show Migrainous activity.
If your doctor doesn't understand Migraine disease, it may be time for a new one. We have a quiz that might help you with this: Is Your Doctor Right for You? After you take the quiz and think it is time to move on, we have a list of patient recommended Migraine specialists you can see HERE.
Good luck
Nancy