Stroke

[JusJenie]

My brother is 41 years old and up until March 2007 was an active, healthy viral man in the prime of his life (normal weight; no history of high blood pressure, cholesterol or diabetes; non-smoker; occasional drinker). Since March 07, he has suffered at least 5 “strokes” and numerous “TIA's”, each one leaving him more debilitated than the last. He is under the care of a neurologist who has ordered just about every protocol testing and assessment and has had numerous MRI’s and CAT Scans, all of which are negative or inconclusive at best. Currently, his treatment includes prophylactic medication in hopes of preventing future “episodes”, but achieving and maintaining therapeutic levels have been problematic. There is not history of stroke in our family. It seems unlikely that someone with my brother's medical history should be suffering from strokes and feel that something else may be going on. Has anyone experience a similar situation or know of someone with similar symptoms and background? Also, is it possible to have suffered a stroke and NOT have it show up on a Cat scan or MRI?
I am desperate for answers but to date have not found any. I feel helpless and watching my brother deteriorate before my eyes is killing me. Any thoughts, suggestions or recommendation as to do next would be greatly appreciated.