--is that he could be "co-morbid", that is, he has symptoms from more than one cause and they are exacerbating each other.

In neurology, there is something called the "double-crush hypothesis"--that is, soemthing external, such aas diabetes or autoimmunity, compromises herves enough to cause some degree of symptoms, but then another aspect, usually a mechanical compressive force--carpal tunnel, disc bulges presing on nerve roots (known as radiculopathy), or some such--affecting the same nerves results in symptoms that are more than the result of the component causes.

It certainly seems he has enough compromise in his spine to produce neuropathic symptoms alone. But they may be exacerbated by impaired glucose tolerance/diabetes, or some other cause that hasn't bee found yet. There are over two hundred KNOWN causes of neuropathy, and it seems his situation warrants a much more extensive work-up. I recommend the Liza Jane spreadsheets:


www.lizajane.org

These were put together by a bunch of us (and coordinated by Liza Jane) as the most comprehensive listing of potential tests for neural symptoms we could come up with--excellent for suggesting aveneues of testing to physicians and for tracking test results/patterns over time.