If Your Mother is progressing in disability while on Tysabri, then I would say it's not working for her. It seems the Doc may agree, if he/she wants you to make a dicision to change Drugs?

There are new drugs coming out and may or may not help her. Not all of the MS meds work for all...actually just a small percentage seem to get the full benefit of any given MS drug.

Good wishes and good luck on your journey to help your Mother manage her disease..