I have had a concussion as an 11 year old, and have absolutely zero memory of what happened or how. It probably involved my bike, since that was outside when I somehow stumbled back home (which I also don’t remember).

My brain goes from two or three days pre-concussion, to having the absolute worst time with my parents waking me every hour at night for no clear reason and my arm being broken.

It was not a fun time, and a helmet would have probably prevented that. There’s no permanent damage, i think, but that was extremely lucky.