Hi Melody,
I'd like to suggest avoiding a sural nerve biopsy.
I've had one and life has never been the same.
It's been many years and that area still burns like crazy. I could not wear a full shoe on that foot for over 3 years and was in constant severe pain. I have long-term complications from the nerve injury (from the sural nerve biopsy).
Some neurologists specialize in different diagnoses. You may find a neurologist specializing in CMT nearby? These specialist usually know of the variants, as well.
As always, my best to you and to Alan!

DejaVu