The myelin sheath heals/grows very slowly. It does not close open gaps well. Nerve fibers will grow/heal looking to reconnect with the other side of a break.

Multiple Sclerosis is mainly a auto-immune disease of the myelin. That is why it is so deadly. Remove the insulation and the nerve signals short out.

When nerve reconnect surgery is done, they just have to connect the sheath. The nerve fiber will grow along the sheath.

Vitamin therapy is helpful with the myelin. Omega 3 fatty acids are for the nerve fibers.