That when the time came, he would take care of it himself. That he would not subject himself or his family to a nightmare existence. The brain messages to move all muscles, voluntary and involuntary, break down and finally stop being received. Walking gets worse and worse, taking one from a cane, to a walker, to a wheelchair, to bedridden, to total paralysis. Stomach muscles go so that a person loses the ability to hold the body upright.
Communication is possible by writing, until that skill is lost.
The living nightmare is the throat. The ability to swallow grows progressively worse. Water goes down the windpipe and results in choking. Food goes wrong, also resulting in choking. Liquids are as likely to come out the nose as make it to the stomach.