This picture is going around the interwebs today.
He clearly had his parotid salivary gland removed. (near the upper molars). He also has no upper teeth and a full denture plate. Guessing the lower teeth were natural but rotten, because his chin hadn't receded.
McCain had a similar thing on his other side. Salivary gland infection accelerated his cancer.
Pretty sure the long chronic infections that preceded Fred's salivary and oral surgeries are what caused his Alzheimer's.
Beta amyloid production in the brain is increased when you have a bacterial infection. After a while your brain just clogs up from the excess.
Oh, by the way his son has the same problem. (another related post)