Up to 50 per cent of all small fiber idiopathic neuropathies are ultimately determined to have some glucose involvement. That doesn't mean this is the cause of your sfn, but getting a 2 hour glucose tolerance test is mandatory; some believe a new but not yet widely accepted one hour test is actually superior. HB1ac misses far too many cases of pre-diabetes and early diabetes and should not be relied upon. Given your spinal issues (which I share) you have to consider those as a source, though they may not be the real culprit. Do you have compressed, bulging or herniated discs in both your lumbar and cervical spine? Did the PN start in your toes, spread later through the feet and up the calf with subsequent paresthesias in the hands? Did it manifest symmetrically in both feet, ankles, calves, hands? If your PN followed that pattern it is less likely to be of spinal nerve compression origin, though not entirely out of the question. Yes, skin biopsies and nerve ultrasounds, in particular, can be helpful in differentiating the different types (etiologies) of PN, segregating, for example, those of auto-immune origin, malign origin, toxic origin, etc. Well worth getting in your situation. You should also get blood tests for monoclonal protein assessment, using the SPEP, IFE and serum free light chain tests. Yes, treatments can vary depending upon etiology, but there are researchers who make a persuasive argument that at base the proximal cause of almost all neuropathies are mitochondrial/endothelial dysfunctions that reduce and disrupt axonal energy. Some of this, I believe, is linked to small vessel disease that increases with aging, resulting in systemic disease that, among other things, causes axonal degeneration, demyelination, etc. The current accepted standard of care for this is not very effective, unfortunately, overall, when it comes to idiopathic (unexplained) PN, but such substances as alpha lipoic acid, methylfolate, acetyl L carnitine, propionyl L carnitine, B12, D3, etc. have shown some efficacy. There are a few promising things in the drug and device pipeline that may enter the market in the next year to next few years. For anyone with spinal issues that are a suspected or demonstrated cause, exercise, diet, physical therapy are vital, and acupuncture and low-level laser treatments may be helpful. A new magnetic treatment is being used at a few medical centers with early promising results in alleviating PN pain, though whether this modality addresses underlying causes remains to be demonstrated.