I don't think the solanine DAMAGES the nerves. No evidence of that exists yet. I think it is some chemical stimulating reaction. Your biopsy was negative right?
Showing no damage yet...at least not at the levels they measure.

Some PN symptoms are a direct reaction to a chemical...but not all are going to be killing nerves outright.

Some heavy metals can leave permanent damage, herbicides, and drugs, but the histamine reactions are reversible, and I'd expect the solanine may fit into this less serious category.
Food intolerances are pretty common, and when the offending food is stopped, usually the symptoms decline or go away.
An new toxicity example== a study on Round Up weed killer has found it is implicated in generating Parkinson's disease (neurotoxic). And farmers who use chemicals alot have higher rates of Parkinson's as well. So those types of exposures may be more serious and lasting.

People with gluten induced PN, do improve when the gluten is removed. We've had several posters over the years post about that.