I do agree with everything you said, but one thing I need to bring up- no two people that have brain injuries are alike. Some do live productive lives after without much complication. Two people can have almost identical accidents, but it can affect one person and change them completely, while the other is fine. I have seen this happen from sports accidents, car accidents, etc. It is so unpredictable, which is why they need to be monitored closely and medication levels checked frequently.
Of course, this is all assuming that the mother is telling the truth about her son having a concussion, to which may have definitely altered his brain chemistry for life.