EMG/NCV won't show much if upper body soft tissue are causing the impingement/symptoms.
The nerves can be slightly irritated by adhesions or sticky tissues and that will not show up, but it will cause symptoms.

Possibly farther up than only at the wrist or elbow??
Scalene muscles, pec minor tightness, collar bone area tenderness?

any neck or shoulder pain?
changes in c spine curve {hump back??}
posture - forward head, forward or rolled or hunched shoulders?

If any of what I mention makes sense please come read/visit on the TOS forum for more information.