Uncontrolled diabetes is one of the big causes of peripheral neuropathy That’s about all I can tell you about it...starts at the feet cannot reverse it, I am sure his doctor has already tested for diabetes, if he doesn’t have that I would suggest for your own information The Mayo Clinic has a web site and you can search. WebMN also has a site to search for medications and/disease..
Thanks goat granny for your response. No, he's had all the tests, and as I said at the beginning, this doesn't seems to be the cause for him, although that's one of the first things they check for.