Welcome Kristen. I also have only one lesion, and it's in the brainstem. But my spinal tap was positive and I had enough symptoms that my neuro was confident enough to diagnose me as probable MS. I was started on Avonex right away and I am treated just like I have MS. Only difference is that I only have one lesion. and if I am treated with the same respect as one with a full diagnosis I hope I can always keep it probable because it means just the one lesion.