I don't think the researchers really know what happens during healing. There is some thought that the myelin sheath that insulates axons is where much of the damage is. Myelin sheath is slow healing. The actual nerve tissue heals/grows faster but it will not heal/grow without a healthy myelin sheath.

The concept of neuro-regeneration is widely debated. The challenge of neuro-regeneration is the axons and dendrites connect in a haphazard way. If the connection is accepted, it is allowed to continue. It the connection is rejected, the axon is pushed away and it looks for a different axon/dendrite to attempt a connection to. Because of this haphazard connection, it takes a long time for these neural circuits to become functional.

Weak or damaged neural circuits also need to re-establish a proper flow of information. They can become lethargic. Once they are ready to function, they need gentle stimulation to start the flow of information. It is like restoring a memory. It does not take as much effort as the first time the information/process was established. Think of it as a mountain trail that has started to grow over. It takes a slow effort to find and follow the old trail and many repeat trips for that trail to become a well beaten path again.

The only thing we can do to assist this process is to maintain a healthy metabolic environment. This means low stress to prevent an overload that can result in a toxic condition. Researchers are trying to find compounds that help to reduce these toxic compounds from collecting in the brain. The research is just starting but appears to be subordinate to similar research neurological disorders with a greater public outcry, like MS, ALS, Alzheimer's and Parkinson's.