Have you gotten a second opinion? Maybe another doc will concur and you can put your mind at rest and avoid the LP

I was diagnosed immediately as well, but my neuro still requested that I do total blood work up and LP and some other stuff. His MO the first year of diagnosis is to continue to look for other potential ailments just to be sure his diagnosis is correct - every once in a while he still asks me to do some additional testing or see a specialist for something else just to be sure.

I can't imagine being in limbo for years, but sometimes I wonder if I might have handled my initial diagnosis better if I had not been blindsided. I accepted the diagnosis initially then a few weeks later I was certain I was misdiagnosed and was being treated incorrectly. You should do what ever will put your mind at ease about your diagnosis it makes moving forward easier.