First, I'm not a doctor. I do not know if nerves grow back. I don't think they do. Once damaged, that's it.
Second, I can only speak about what I've learned which was for ME. I can only speak about those who have the same or similar situation. Those that my doctor claims have the same or similar situation.

What I'm saying is that the Bracial Plexus (BP) is typically the culprit in TOS. I have heard that the BP is now being suspected for Carpel Tunnel(CT) and that a lot of surgery on the forearm to relieve CT is unproductive because the "cause" of the CT is higher up...at the BP level.

That said, I wish people would LOOK at the anatomy of the BP and where it originates (neck vertebrae...c5 and c6) and how it travels from there and then under the clavicle near first rib and under or by the coracoid process and branches out from there down the arm. If people would SEE that, they might better understand WHY it is that BACK/SHOULDER posture AND NECK/HEAD posture is SOOOOOOOO important to preventing the compression that causes the pain. Look at the structure of the Shoulder Blade...how it SHOULD be aligned and how it may be aligned in YOU. The coracoid process is part of that Sholder Blade. It is a protrusion in front (believe it or not the back Shoulder Blade has parts that protrude in the front of the human body). See that and you can see how the alignment compresses. Look a the plane of a proper shoulder blade. Look at how yours is. Look in a mirror. Ask a friend. Does your wing out? If so, it is NOT being held in proper alignment. This then affects your shoulders, arms and chest. Shoulders that are "rolled forward" typcially ALSO have a chest that is more "concave" inward (think fetal position). This causes compression...less space for the nerves to travel under the coracoid process. If your head is in the "forward" position i.e. not straight up and aligned with the spine...again stain on scalenes which puts strain and compressionon BP. OPEN the Chest...roll the shoulders down and back...reverse the concave and you allow more space for the BP to pass under the coracoid process. Get your PT to show you with an actual Shoulder Blade on a Skeleton...it's amazing the visual as to what needs to be done. Now, that said...this realignment is NOT going to happen over night. It will take a LONG time because your body is USED TO this position...it is a default relaxed position that you have become accustomed to...you now have WEAK pectoral minor muscles dragging that coracoid process down in front so much that your back muscles that are supposed to be strong to fight against that force and hold the shoulder back, becomes stretched out and weak (your rhomboids and mid traps)...it takes time to REVERSE the process i.e. STRENGTHEN the rhomboids and mid traps etc...to fight the pec minors...and hold the shoulder blade in the proper position and do so "naturally" Those of use with TOS have to have better posture and maintain that more often than the rest of the world...it may be unfair but that is HOW we stay pain free. I've been working hard on getting my muscles to keep my shoulders down and back...open my chest and hold that position....I've made progress and it's been about 8 months now...I HAVE reduced the number and intensity of my flare ups....the doctor has measured and found pulses that did not exist before, blood pressure that had been cut off, back again....my posture is improved...not where it should be but better than it was which is WHY I'm getting less flare ups. I still roll forward with certain things and I'm ever vigilent to try to prevent that....the other day someone caught me doing an exercise with my chin stuck out ....NOPE....bring it back...head and neck straight up and in alignment with the back....it doesn't take much but yes I had a flare up because of that 12 hours later...I know what I did wrong...I have to CONSTANTLY remind myself...but I am able to do things now which used to cause flare ups and now they don't because I know what is causing them and I'm watching that posture and alignment. That's all I'm saying.

I don't believe in surgery unless there is NO OTHER OPTION. LAST RESORT. What I'm saying (earlier post) is that too often people are not willing to do the work to fix their situation which is fixable WITHOUT surgery. Many doctors and chiropractors and PTs have said this. People give up because they want IMMEDIATE relief and can't wait the 6 months it might take to start to see that the exercises and posture improvement DOES work. If they dull the pain by pain meds instead of doing the physical work, the muscles WILL atrophy. They need to be used, they need to be strengthened. One of the posters in the other thread realized that his bench pressing was the OPPOSITE of what HE needed. I too learned this. You do NOT need STRONG PECTORALs. They are already overwhelming the back by pulling in front....Bench pressing strengthens the pectorals...what he learned is to stop the bench pressing and STRENGTHEN his BACK muscles to counter act the strong pull of the pectorals. You want the back muscles to pull the shoulders BACK...you don't want the pectoral muscles to pull them forward and down. OPEN the chest. Pinch your shoulder blades back. By dulling the pain you are not addressing the CAUSE of that pain, the PHYSICALITY. Eventually you get more concaved and more compression to the point of ACTUAL nerve damage. That is what happened with this woman I mentioned before. That led to surgery because she felt THAT was the only thing that would relieve the compression...remove a rib!!!!...guess what...it didn't work. Why because her body had become SO BENT forward that the muscles and nerves were already permanently compressed on each other....the rib(s) weren't what they were compressing against. She can't straighten up...She is too weak to try to get back to where she once was. I don't want that for ANYONE.

Yes, you have to be careful when exercising...because you can damage the nerves...but if you are careful and understand what is GOOD pain (and yes there is GOOD pain) and what is BAD pain...you can get better. I'm convinced. Maybe I have it easy or easier than the rest of you....or maybe I have worked hard to prevent surgery and get better. I don't mean to sound self righteous....as I said...this worked FOR ME! I'm convinced it will work for many others. It does take WORK, PERSEVERANCE and PATIENCE. For me the patience was the hardest part.