According to recent article in the Journal of the American Medical Association by Scher, Ann a study in Iceland has shown evidence that women who suffer from migraines with visual auras were twice as likely to have lesions (damaged areas) in the cerebellum later in life. The cerebellum is part of the lower brain that participates in balance and movement. It is not known if these lesions have any effect or significance.
These are interesting findings in light of the evidence that some people who suffer from migraines also have effects (small areas of vision loss) in their peripheral vision. To the best of our knowledge, these defects are inconsequential on overall vision. The advent of automated testing of peripheral vision brought these defects to awareness, patients have not complained of symptoms prior to the findings. Perhaps the cerebellum damage will fall in the same category, interesting findings on MRI tests that have no effect on overall health.
The larger question is why these problems occur. Conjecture would be vascular, or blood flow changes associated with migraines but migraines are not strictly vascular changes. Hopefully understanding these complications can lead to better understanding of migraines and preventative treatments.
Any severe headaches associated with flashing lights, loss of vision, or other vision symptoms warrant a visit to your eye doctor and family doctor, with further evaluation by a neurologist if needed. Migraine headaches are considered a diagnosis of exclusion, meaning after every other potential cause has been ruled out they can be diagnosed. Usually there are specific characteristics that help in making the diagnosis after a complete evaluation, but occasionally they can have complications that resemble strokes or other neurological problems. Vision insurance such as Vision Service Plan often provide coverage for vision exams associated with migraine symptoms. Because other serious problems like retinal detachments can cause flashing lights you should immediately call your optometrist if this a new problem that has not been previously diagnosed.