If all the usual suspects have been rounded up and eliminated, many here DX as Idiopathic. That means no known source or causal factor. If you have lurked around and read, you know that PN can be triggered by many things. Vaccine shots, Industrial solvents, Chemotherapy, Spine & Joint trauma, Floroquinilone Antibiotics,environmental contaminants plus Tick bites. Lyme testing, as I recall, is not the most foolproof thing. Good Luck, Ken in Texas. P.S. These are not all the things that bring PN, just the ones that jumped to the front of my mind.