I am on Medicare now but the first two years of my illness was with private insurance.
My experience with my case manager was very positive. As long as I thought they were helping, and they were, she continued to approve them.

I hope that between your Dr's. recommendation for the treatments and the fact you can tell how much the IVIG helps and you can feel it wearing off will be all she/he will need for you to continue.

Good luck;

scrubbs