This is common. Due to the cost, insurance companies (all of them) review the medical necessity on a regular basis. They will stop it every chance they get to save money. If you have documentation of PN or small fiber neuropathy based upon a skin biopsy, emg, or ncs, then you shouldn't have any problem getting the treatment continued. However, if your doctor ordered this based on just 'symptoms' or only labs showing an autoimmune disease, then your case will be much harder to prove necessity.

Not knowing anything about your case makes it hard for me to answer your question about what type of 'help' you can do to get this headed in the right direction. But in general, gather all your documentation for any/all doctors involved in your care that would support your diagnosis...ie, labs, tests, doctor notes, etc. Then contact the insurance company about appeal procedures and follow them to a tee asking for a reconsideration.