IIUC, fixing severed nerves in the spinal cord is beyond the state of the art in medicine.
So when someone goes to the ER with a cut-off finger, how is it possible for the finger to be reattached, and for the proper nerve connections to be re-established?
The peripheral nervous system can regrow nerve tissue but only if it has an intact pathway. So when they sew on a finger, if they can repair the myelin sheath, new nerves will grow down the old conduit at a rate of about an inch a month.
So they sew your finger on and you have to wait a few weeks to see if you're going to get any feeling back. That waiting would drive me nuts.