While I haven’t been in that particular situation, I did spend over a year in limbo, and found that there is a ton of variation in how aggressively neuros pursue further testing. Are you familiar with the McDonald criteria for diagnosing MS? As far as I can tell, these are the most current guidelines for diagnosing MS, and I found learning about them helpful.
If you are interested, there is a lot of information out there if you do a search on “McDonald criteria for diagnosing MS”…or something like that. I found the two articles below explain the diagnostic process pretty clearly, and the information they contain seems pretty consistent with what I found on more well-known sites.
(Mods…I think these kinds of links are okay to post?)