My doctor called me in but I had several tests before I received a diagnosis. I haven't heard of many peope receiving a diagnois from just an MRI. Many things can cause brain lesions and those all have to be ruled out. I had a brain, cervical spine and thorasic spine MRIs. I had a lumbar puncture, evoked potentials (extremeties, hearing and vision), blood work, a neurological exam. After all that, I was diagnosed.
Good luck. I hope you get good news and it is something very treatable.