A lad at work got jumped a few years ago and suffered a concussion, got the all clear at hospital but over the next few days his speech and demeanor were just like Max's, he also had a little bit of an issue controlling his leg properly.
Eventually we made him go back to the hospital, they gave him another scan and there you go... Two blood clots, they drilled a few holes in his head and washed water over his brain to clear the clots and he's back to normal...apart from the big fucking dents in his head.
Not sure how that would affect a fighters career long term because there's no ongoing care or medication.