I don't know what an SO is? One of the ways you can help us help you is to present a coherent picture of exactly who this person is. Okay, I know it's a male. And he's a patriarch, so I'm guessing he's over 35. But beyond that, I'm clueless as to a sense of his medical history. Can you fill us in on more details of who he is--history of diabetes, family history of diabetes, obese, other problems---arthritis, heart, balance, deafness; family history, drug/alcohol/toxic exposures?

Everyone who has posted to you already has done a fabulous job of outlining the various issues involved in diagnosis. Somewhere there will be a cause, most likely.

I've posted a list of all the tests which can be done, and most should be done, to make a diagnosis of neuropathy. They're posted at www.lizajane.org.

You'll find there links to spreadsheets. Each spreadsheet lists a group of tests. Some of tests for hereditory pn, some for immune pn, some for toxic. The ones for sensory pn are separated from the ones for motor. Plus, there's a list for sensory and motor neuropathies that can be used somewhat like a to do list. I'd suggest poking around there and then downloading the charts which apply. They can be brought to neurologists to help feel you've gotten completeness. Also, I very much recommend asking for copies of the results of all tests when leaving each doctor's appointment.

The spreadsheets are useful for anyone, btw. They help people keep track of yearly tests, or tests specific to their medical problems, in a way that makes trends easily visible.

Good luck helping your SO.