While you sometimes do not have health problems beyond your brain injury.
There are some of us that do.
Brain Injury (TBI or ABI) has particular functions to each brain.
Yes! I believe Severe concussions come back!
Mine did at 60 years of age!
Wow! Trigeminal Nerve cane into my life like the most painful painful experience. It is hard to explain how bad the nerve comes back.
Here are some pictures from Wiki that I retrieved.
The blue is the major section and that is a bear that hurts till you can not think anymore. I had mine Gamma Knife out by The Brain Expert in Atlanta, GA.