Hello and thank you for your time reading this.
I am writing a feature film screenplay, where main character is suffering concrete medical conditions, which is essential for story development. Lack of my medical knowledge do not allow me to be accurate and I would like to hear your thought if a case like this exist in a medicine or could possibly arise somehow.
My main character (male teenage, almost 20) looks completely normal, but his head (or him completely) is somehow exposed to external injuries. Even a slightest head injury can damage his brain (or any other head section) and cause far more serious consequences than any normal human being (for example, in my story he gets severe form of amnesia after falling from a stairs, unable to learn new things after getting hit by a ball in a head while playing with kids, and gets temporarily paralyzed after falling from a tree). Because of this “illness”, his parents have to isolate him in a room and cover everything there by a soft material to avoid any injury. He is forced to make a dramatic decision as to stay in a specially designed room for him, safe, and completely isolated from world or to go outside, run, play, have fun and risk his health.
If you can, please provide me with some useful information if a condition like this could exist. If something like this cannot happen, any disease or condition close to this will be extremely useful for me. It can be extremely rare, or even partly a fiction. Something that keeps human being lonely and in isolation.

Thanks in advance and best wishes.