I smoke marijuana for medicinal purposes but after my brain damage it now has adverse effects, will I ever be able to smoke it again?

Total unknown. With out knowing what is the medical purpose that you are treating with medical marijuana, and the reason for and the extent of you brain damage, it is impossible to say. Hopefully you are being treated by a neurologist, they should be able to give proper guidance. If you don't have a neurologist have your medical doctor refer you to one.