Welcome to NeuroTalk.

This condition has a complexity that others do not. There are over 100 causes of PN, and determining which is the culprit, can steer you toward some solutions.

Some are topical... like Biofreeze, and epsom salts. Some are nutrients, there are many more besides B12.

Can you tell us more? What drugs does he take? Some drugs deplete nutrients. Some drugs CAUSE PN... and doctors are hesitant to reveal this.

Where is his PN? in the feet, all over ... where? Do other family members have it?

Most people and doctors too, don't recognize that frank diabetes is not necessary for PN to start. The low blood sugars that precede diabetes can starve and damage nerves while tests show "normal". This is called impaired glucose tolerance.

Does your father smoke? Does he have PAD, Peripheral Artery Disease?

There are poisons all around us that damage nerves. Pesticides, herbicides, car exhaust, solvents.

Autoimmune issues including gluten intolerance may affect nerves. Autoimmune issues in males begins more commonly after 45-50. (although today more younger men have them too).
Autoimmune issues may be triggered by vaccines.

I assume since he has been to Hopkins he has had autoimmune testing?

Long lasting PNs should be screened for gluten intolerance.
Continuing to eat gluten containing foods, in a person who has become intolerant can lead to nerve damage:
http://sites.google.com/site/jccglutenfree/
The link above has a special section on gluten and neuropathy.

There is alot of information here that we have all gathered over the last 4 years, so check out the subjects in the subforum above here and see what strikes you as familiar.