I'd suggest seeing a physiatrist or Physical Rehab Medicine specialist. They conduct EMGs/NCVs. It was a physiatrist who diagnosed my TOS. I had shoulder and have spine problems making me a complicated case but he tackled the most obvious first => TOS. My experience with the physiatrist was he acted like the center of a wheel, managing my care with several different providers. My chiropractor dismissed TOS as a possibility when I mentioned they were looking into it as a possibility.