--from the Greek "poly", meaning many, just means "many nerves", and "idiopathic", from the Latin "idio", just means your pathology is, for now, confined to self--there is no known cause of it. Your diagnosis hasn't really advanced anywhere with this, although doctors do need SOMETHING to put down on insurance forms.

Hopefully, the further testing may reveal something that can point to a cause--be sure you get and retain copies of the test results!