This make perfect sense now. And with your family history, he should check large fibers, just in case.

In most cases the 'cause' only gives us piece of mind that we know what it is...it doesn't change the outcome. But in some cases, the treatment may change, so always good (I think) to explore some of the causes.

All depending on how long you have been taking the zolpidem, you may experience some withdrawal symptoms if you just stop taking it.