This is a possible question for the RSD forum, I think.

They have "sympathetic" spread, and mirror pain, has been discussed there.

This is a beginning article on mirror neurons:
http://en.wikipedia.org/wiki/Mirror_neuron

I don't think it is definitive yet, but spread of pain in RSD which is a form of neuropathy, is thought to be centrally located in the brain, by some researchers.
Also there are studies now showing Vit C can block the development of RSD...when surgery or trauma happens to ankles and wrists (ankle injuries are common first sites of pain for RSD patients).

Whether it is a "chemical" spread of inflammation, or a CNS brain change in pain perception, or both in some way, is still not understood.

RSD neuropathy seems to be a circulation problem. In early stages use of calcium channel blockers helps, which dilate blood vessels. There are papers on nifedipine for example. Also RSDers hate ice treatments and claim it makes the pain worse. They use heat much more than PNers do. Most of the PNers like ice or cooler temperatures, or cold water soaks, for example. So while they are both "neuropathies" the actual mechanism of causing the nerve pain seems to differ quite a bit.