Did you check on SSDI ? It is a federal government program.
We have a SSDI forum if you want to explore that & the sticky threads there for more info.
https://www.neurotalk.org/forum28/

I believe there is partial or % ratings , and also you can earn under certain amounts or do a return to work program..
Most suggest doing a self application online ( of course only if the requirements do fit) and if that is denied then an atty can be used for appeals.
It doesn’t need to be a forever thing. if he improves with time off /or part time work he can return to full work..
*just a quick synopsis of my reading there*

* do a site search for - scar tissue ( it can occur inside the body after all the trauma - some people have much more issues due to it.. )