It's really frustrating when you can't get a definitive diagnosis.
But, it seems neurological disorders in general are very difficult to diagnose. Often, there are no lab tests, MRI scans, or surgeries that can tell the doctors exactly why your seemingly intact nerves are not functioning properly. Even the symptoms (such as pain) are difficult to interpret since they can't be physically measured and rely on the patients description. So, all the doctors are left with is making "educated guesses" based on your history and symptoms.

Hopefully there will be breakthroughs in this area soon. Unfortunately, it will probably be too late for most of us to benefit. But, at least our children might have access to better diagnostics and treatments in the future.