I think so, yeah. They could confess "and any sins I have forgotten" just to cover their bases, but it's impossible to have true contrition for something you don't remember having done. I don't think they'd repeat confirmation since it's not one of the repeatable sacraments, but in practice the priest would probably have some kind of little "renew your baptismal vows" thing for the person, if they wanted it.

(These are hypothetical questions that have very little to do with the actual pastoral response to head injuries, but they're fun to think about)