Yes, it is a cascade of bad chemistry that messes up the brain. The physical damage makes the brain less able to properly metabolize energy and use nutrients to make neurotransmitters and such. The waste flushing system called the glymph system, similar to the lymph system in the rest of the body, is extremely delicate. It is so fine that it was not even discovered until a few years ago. This clogged or damaged glymph system may be why DTI MRI's can recognize abnormal flows of fluid in the white matter in areas affected by injury.

https://www.urmc.rochester.edu/news/...-in-brain.aspx