I personally believe the mitochondria are damaged mostly by antibiotics.
This is where much of the research is.

Many antibiotic drugs kill bacteria, and mitochondria are actually bacteria who live in our cells, as symbiotes... some ancient plan where they joined with other cells to provide energy for the organism.

But toxins may poison them too. Once a cell cannot make energy it stops functioning properly.

Free radical damage also is implicated. This is why antioxidants work for aging and PN I think. Oxidation by oxygen free radicals.

Thanks for the article. It really helps to have a mental picture or framework to see how PN problems really are. Otherwise it seems rather nebulous IMO.

Here is a link showing what Schwann cells are:
http://en.wikipedia.org/wiki/Schwann_cell