You need to see a neuro that is a PN specialist.
One in a teaching hospital neuro dept that does research,
or a facility that has a large neuro dept with experts in PN.
I go to Johns Hopkins. There are other centers like
Jack Miller, The Cornell-Weill Center, Mayo Clinic, etc, that
will do this.
Most plain neuros will take your money, and are clueless
as to proper diagnoses, treatment, & medications.