I think everyone overlooks this. Even though NGF is more important to sympathetic growth during early development, it still matters for surgerys like ours. I've been taking some supplements and stuff to increase Ngf recently, and have seriously had a small amount of sweat return to my hands. 
PS: could the difference between developing and developed growth from NGF be that we have Schwann cells to grow into ganglia? So maybe NGF and stem cells could reverse.