The Harlan Lebo book (The Godfather Legacy) mentions that the make up person in Sicily was not very good and the jaw bruise was not done too well. As far as the affect on his speech, sinus, etc., I'm sure a well-placed punch can do extensive damage.
Exactly. A little knowledge of physics and anatomy will explain alot. The book states that Mike had to have bits of bone dug out of skull and his jaw had to be wired. People just don't understand the physics of a punch delivered to a relatively immobile person by what is essentially bone - a fist. The destruction of capillaries, muscle tissue, fat tissue, and bone can be immense and the effects last for months or never be returned to normal. The impact on the jaw will send alot of energy through the neck and down the spine which could have even worse effects. By the way, professional boxers wear at least 10 oz gloves and they tape their hands because the gloves don't offer all the protection to their own hands that they need.
