I had my regular MRI done in June and thought nothing of it. After all I have to have these every 4 months to monitor how things are going. This is because I am having monthly Tysabri infusions which are pretty strong. They also closely monitor blood tests for various things including JC Virus. I am positive for this virus which puts me at higher risk of getting PML (Progressive Multifocal Leukoencephalopathy) - a very nasty potential side effect. So they monitor me closely with regular MRI's.