There is a considerable amount of information if you go to "google" and type in:

Glossopharyngeal neuralgia, multiple sclerosis

I read most of the info on the first page of references that came up, and there was some interesting things to consider; differential dx, potential for it to be something else very similar (considering the person has MS), etc. It's worthwhile to look into this . . .

Sorry about your friend, whatever is causing it. I had a numb mouth, tongue, throat and lips for several weeks one time, and it was scary enough.

Cherie