On the GMI +...it is an antineuronal antibody. Seems to me, that you are in the middle of a diagnostic journey that could potentially last a while. Here are are few references that I have found. I wonder if a muscle biopsy is another test that may be enlightening.

http://www.nni.com.sg/MedicalSpecial...larLaboratory/

http://www.genengnews.com/news/bnite...?name=49795740

The neurowustl site below may help. Many of your antibodies seem associated with neuronal disease.

http://neuromuscular.wustl.edu/antibody/pnimdem.html

IVIG is used a lot in neuronal disease, small fiber and demyelinating.