My brother had pain in one of his arms. Eventually he started losing muscle in that arm pretty badly and went to see about it. He had a pinched nerve in his upper neck somewhere caused by too narrow opening where the nerve came out of the spine. He had the operation to enlarge the opening and is now doing fine. It took him quite a while to get the muscle back in that arm that he lost while in pain. I guess he was around 72 or 73 at the time that was several years ago. Doctor thought it was genetics that some people just naturally have smaller openings where the nerve comes out. As we age the spinal discs compress and the ones with this smaller opening get the nerve pinched as the disc space gets narrower. That was his theory at least as I recall what my brother told me about it.