I wrote you this big long post about anaesthetics and it has vanished with no trace into th eblack hole of cyberspace...
So, in a nutshell, I have had a spinal anaesthetic since having ms and it is no worse than the spinal tap that most of us get at the beginning, with similar potential complications (also possible allergy to anaesthesia used but very rare). It worked brilliantly - no pain during operation and for a few hours afterwards, then au and about that evening - no nausea and grogginess that you get with a GA.
To me, there is no logical reason for not having a spinal anaesthetic if you have ms - they are happy to do spinal taps which deplete the spinal fluid cushioning the brain - spinal anaesthetics introduce a substance into the area around the cord, but below L5 and it will not rise above this level (about top of your hip bone level). It was no problem for me, and may not be for you either - chat to your neuro to be sure, but mine was happy with it and I had no after effects or relapses.
Even if you have a GA - best place to be is in theatre with a ventilator if you have sleep apnoea.
I know you are probably nervous but sure you will be in safe hands.
All the best