Why is peripheral neuropathy skin punch biopsy taken from the calf instead of the foot?

--because the original normed figures that intraepidermal nerve fiber density ranges were based on (the original work was done at Johns Hopkins) came from groups of subjects in which the density was measured at lower leg, upper thigh, and right above the elbow.

The original Johns Hopkins researchers chose these places as they are standard places of hairy skin with at least a thin fat layer, meaning it was easy to take the samples and there were few structures to get in the way or compromise the measurements.

It is possible to take samples from anyplace there is hairy skin--I know a few people who've even had it done on the face--but it's much harder to interpret the results in these areas as normative levels of nerve fiber density are not well known.

But what if my neuro only took a biopsy from both calves and not the ankle or upper leg.

--with known values from "normal" patients at that location.

Still, more comprehensive testing would involve the other sites as well--and doing the biopsy at multiple sites might also show whether any reductions in intraepidermal nerve fiber density were dependent on the length of the nerves, which can have some diagnostic value in some cases.

I also suspect they don't do the foot, because injuries/wounds on feet don't heal well. Many PNers have diabetes, and part of their monitoring is to avoid injuries to the feet!

Rec'd my biopsy results. Test results say "Density of epidermal nerve fibers in normative range."
However, I had "degenerative changes within epidermal nerves." "These findings are often predictive of the future development of clinical neuropathy"
"Mild Morphologic degenerative changes are seen among intra-epidermal nerve fibers."
"Epidermal nerves are mildly patchy in distribution.Occasional epidermal nerves are varicose in appearance."
It goes on and on about the microscopic description.
I failed "Tinel's Sign" diagnosis and EMG studies were inconclusive.
(I failed one foot and passed the other)
Neuro thinks Tarsal Tunnel and favors injections or MRI next.
What do you guys think?