Ditto what Aussie said!

See how the IVIG goes. If the insurance takes is away, then you can try the Cellcept or other. Personally I don't think they will take it away with your documented Dx. I receive IVIG for CVID and Autonomic/peripheral neuropathy and no problems for the last year of getting it. Of course CVID is a primary immune deficiency so easy to get, but know many people that receive it for neuropathy only without problem. Insurance has settled into the idea that this is a recognized treatment protocol for neuropathy...with success.

But at this point (9 months later) you should know whether the IVIG is helping your symptoms. If so, then push to keep it. Of course not so easy to gauge whether it is slowing or halting progression.