I believe the stats for complications from contrast are 1/175,000 or something? Yes, there is a very slight risk.

However, you should get the contrast. They won't be able to determine if your lesions are active without the contrast. Without the contrast you could also be increasing the amount of time you spend in medical limbo. If you get contrast enhancing lesions in your first MRI it could save you the fun of things like spinal taps to get a diagnosis.