I had a stroke in 2007 and have had several stroke like episodes since than. My neurologist is calling them silent migraines and nor more mini strokes. The last episodes have not showed up on the MRI as a stroke like the first one did and now says they are silent migraines. I have a light show in my eyes before they really set in full blown with all the things that happen when you have a stroke. What medication does one take as a preventive for these occurrances?