Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is nor can I make specific recommendations. However I will try to provide you with some useful information.
As you know, vasculitic neuropathy is diagnosed based on the history, examination, and often most importantly, nerve biospy. Lumbar puncture is important as well. Excluding infections or toxic causes to the neuropathy is important, as is excluding a vascular cause (ischemic neuropathy due to poor blood flow to the extremities as occurs with peripheral vascular disease). Rheumatologic evaluation, sometimes repeated evaluations several months apart, may be necessary before a cause is found, if one can be found. There are of course many many causes including polyarteritis nodosa, Churg Strauss and Wegner's, cryoglobulinemia, infectious, cancer-associated, and the systemic vasculitis that affect the nerves. Sometimes, no systemic symptoms are present, though an underlying rheumatologic disorder is present.
Once the diagnosis is confirmed, immunosuppressive therapy is the mainstay of treatment as you know. It sounds like you have not had a good response to these medications; the question when one is assessing response is really twofold: is the neuropathy stable/not progressing? and are the symptoms improved? if the neuropathy does not progress (does not start to involve other nerves, spread upward etc), even if it does not improve (even if the damage is not reversed) this may be indicative of a response to therapy, even if there is still severe neuropathic pain. When there is not a good response to immunosuppression, another question is whether or not the diagnosis needs to be revisited, and other, non-inflammatory causes investigated.
If the pain persists, then treatment sometimes requires several medications at once; involvement in a comprehensive pain program is helpful to many. There are several other possible treatments to neuropathic pain. As with other conditions, medications that were originally invented for other purposes are useful for pain. This is true of neurontin and lyrica which were originally invented for seizures. Lyrica is similar to neurontin but has less side effects and often people who can not tolerate neurontin benefit from lyrica. However it is more expensive. This is also true for medications such as amitryptiline, which was originally used for depression but is now a mainstay of treatment for neuropathic pain. However, it has several side effects and may not be used in patients with heart problems.
If the rebuilder therapy is useful to you, it may be worth a try, though it is unlikely to affect the disease itself, if it provides you relief, it is unlikely to be harmful though again this would ultimately be the decision of the prescribing physician. It may sound simplistic, but swimming, and specifically water jogging, has been found to be helpful for the symptoms of neuropathic pain due to neuropathy.
Continued followup with your neurologist and rheumatologist; and evaluation at a tertiary care center (a university hospital in your area with neuromuscular and rheumatologic specialists) would be of benefit to you if this has not already been done.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
I had necrotizing vasculitis (polyarteritis nodosa) six years ago and was treated with cytoxin (cyhclophosphomide) and large doses of prednisone for six months. After that I was diagnosed with mononeuritis multiplex, which causes peripheral neuropathy, among other things. Have you been hospitalized for your vasculitic neuropathy?