CLstewart I was diagnosed with this a few years ago but have suffered from the condition many years before I got diagnosed. I have had a difficult time finding effective treatment for it. Tried IVIG a couple years ago and got aseptic meningitis after 5 treatments so had to discontinue. Tried plasma but this made my neuropathy much worse, as I have also been diagnosed with autoimmune autonomic neuropathy and motor neuropathy.
I have tested positive for GAD65, N-Type Calcium Channel antibodies, GD1a ganglioside antibodies, and positive skin biopsy for small fiber neuropathy and have consistently elevated CPK levels.

It has been a frustrating road and I have unfortunately been deteriorating over the years due to difficulty in finding treatment. While I do find some temporary relief with benzos and alcohol it seems that the symptoms come back with vengeance when the drug wears off. Overall i end up much worse for having taking even small amount. Even with continued dosing i find there is an unavoidable backlash in symptoms when using Gaba enhancing drugs, particularly benzos so I've opted to not use benzos on a regular basis, however i do use it sparingly on a needed basis for temporary relief of bad spasms and contractures. Will most likely be retrying IVIG again sooon and hope to see some improvement with this. Prednisone has not been much help.

Wish I can offer you more insight or suggestions but as you probably are aware it is not an easy condition to deal with. In my case I feel there is a trigger to all the antibodies, the Stiff Person, and the other autoimmune symptoms and i believe it is either being caused by an infection, likely viral, but due to very limited diagnostic tooling in the area of viruses I don't feel too hopeful that it will ever be found.

Hoping to hear from more SPS'ers on here about what has or hasn't worked for them. Have you found anything helps your symptoms? Also curious what you think may have triggered this condition for you?