Re: cortisone injection
Your situation sounds a little like mine. I had carpal tunnel symptoms for many years, the NCS was negative. Dr. did as many conservative options as he could, to no avail, so I had it operated on as he believed I had carpal tunnel even though the test was negative. Pain free for 8 years...have always been very happy I had surgery.
Now the pain is back. Dr. sent me for another NCS and EMG, both of which were negative. He said he still believes it's carpal tunnel, even though it's rare for it to come back, and rare to have a negative NCS (but the surgery did fix the symptoms, so I do believe him).
He wants to do a cortisone injection, not to fix the pain, but to determine if surgery will help again. Similar to what your dr said, he said if the pain goes away, that confirms his diagnosis of carpal tunnel and makes me a good candidate for a repeat surgery.
Like you, I'm at a loss. Don't really want surgery again, don't really want the injection. My dr. is very convinced it's carpal tunnel, I'm not so sure it is...symptoms are not entirely the same as before...I think he may be jumping to carpal tunnel b/c I've had it before. Just not sure what it could be. I think I'm going to seek a second opinion from another dr (although he encouraged me to do so and said another dr will tell me the same).
Good luck - it's so frustrating just wanting to be pain free and know what's causing it!