I have a vague memory of being told in biology that we're born with x number of nueron cells and we can not replace them when they are destroyed.

So would that mean the answer to your Q MD is that as far as the nervous system goes it's an adaptation rather than a replacement of the damaged cells?

Perhaps if the adaptation is good enough maybe that can be a type of healing itself though?

So I guess if I keep impact low the nervous system won't have any good reason to go nuts and make me uncoordinated as a consequence and hopefully it'll get better.

Thanks for explaining and please don't hesitate to correct me if my understanding is way off. 

CC you both