Yep, I used to work with a guy who was as pleasant a person as you would ever want to meet. One day someone walked up to him and punched him in the head. No one ever knew who did it or why. Even him; he had no memory of it. He didn't come back to work for six months, and when he did, it was like he'd had a lobotomy. Clearly he didn't remember me, though he tried to act like he did. The personality, intelligence everything about him was gone. He was a completely different person.
Getting sucker punched is bad. A man in our neighborhood took his twin girls to a concert. Somehow he passed out (not from any drinking or anything), he just got light headed. He hit his head on the cement. Now he can’t work, he has gained a bunch of weight and he cannot concentrate at all. It is so sad for him and his family.