Even going to a specialty center is not a guarantee these tests--the ones that exist, anyway (there are probably a number of hereditary conditoins that involve neuropathy which have not yet been linked to anomalies in the genome)--will be performed. One has to be one's own advocate.

See:

http://neuromuscular.wustl.edu/time/hmsn.html

http://neuromuscular.wustl.edu/time/hsn.htm