Thanks for replying / asking.

In the classification system, my TBI was "very severe" which usually has a basket of 3 criteria, I believe. They're Glasgow Coma Scale score at the beginning, then length of coma (though many people can have a medically prolonged coma, = "induced coma" -- to relieve intracranial pressure, which can further injure your brain squeezing itself up against the inside of your skull), and then length of post-traumatic amnesia (= how long after the TBI it takes to track anything day by day). I scored bad enough on those three.

I don't really know how my MRIs looked at the time -- presumably not good -- but a reason came up for some more MRI-ing about 2-3 years after (and I believe your brain changes a lot over time, in the immediate aftermath of TBI-ing). Those later MRI images apparently showed extensive scarring in the frontal lobes.

It seems to me (from people I've met over the years) that both the severity measures and the MRIs don't necessarily foretell "outcomes". Generally, the worse they are, the tougher things will be, but it seems like it's a loose sort of a match-up. For example or in general, some people who say they had not-so-serious injuries and have clear MRIs don't do well, while others can be the other way around. Acute measures and MRIs may be the least bad predicting tools so far, but they're not great.

My physical symptoms were VERY light. In only the early months, I was very clumsy and poorly coordinated (and I could get to feel nauseous) but that got better, (although I wouldn't have stamina). As I understand it (which of course I may not perfectly), the physical "command posts" in the brain and coordinating spots are fairly localized and discrete. Anyway, my physical signs/symptoms cleared up. ...There's another issue about perception of physical risks, plus speed-control-coordination, which we may not be good at, but the other issue would be about deciding/planning to risk-avoid, which is pretty important.

+ I had one later concussion, knocked out for some time -- I don't know for how long but probably less than an hour before I was found. I went to A & E, was able to tell them that I'd had a previous, but they did zero in testing/assessing/scanning, and I was too zonked to appeal/ask/repeat things. I think I was pretty "lucky" (how I hate that word!) with re-concussing and I got to feel ok after just a couple of weeks -- but it did certainly convince me to stay away from physically risky activities, with which I'm very content. That re-concussing was 8 years after the bigger original TBI.