There is some evidence that the brain has a system that tries to recover from injury but after a while, it may recognize that certain parts of the brain are not able to recover. At this point, it sends out die signals those cells die and are absorbed. Now, the brain has to learn to work around these broken areas, if it is possible. My neuro stated this in a 'recovery reserve' way. For some, this recovery reserve can take over. For others, this recovery reserve has already been used up. This would fit with the Multiple Concussion Syndrome process when after a number of concussions, recovery is haphazard and prolonged with some symptoms remaining.

The other issue to consider is that some concussions are just in the brain. others include upper neck injuries that impact how the brain recovers. Until those upper neck injuries are treated and healed, the brain continues to struggle.

There is what is called a brain stem concussion. This can have some difficult symptoms with some dysfunctions that last.