Jimmy (77) wrote about his son's battle with the illness as a foreword for new book Against The Odds by Andy McGovern (79), Ireland's oldest survivor of the condition.
"His deterioration was rapid: in succession he lost the use of his arms, legs, feet, hands and voice, until, for the last five months of his life, he couldn't speak, couldn't shake his head, couldn't point a finger," Jimmy said.
"The only thing he could do was smile. I will always remember him for his smile.
"If you told him a story he thought reasonably funny he would smile. If you asked him a question and the answer was, 'yes,' he would smile.
"He had no way of communicating, 'no'." Jimmy's son was painfully aware that there was no cure for the terminal illness but he decided to donate his brain to Beaumont Hospital for MND research.
"I would love to see it playing a part in achieving a breakthrough for this terminal condition," Jimmy said.
"For me, this would be the greatest legacy that any of my family could leave the world."
Jimmy said that Paul's battle with this relentless disease showed his family and friends, the true meaning of the strength of the human spirit.
"The same quality, over a much longer period of time, is evident in every page of Andy McGovern's memoir," he said.
Jimmy's colleague in RTE Sports Colm Murray (60) was diagnosed with MND in 2011. The colleagues of both men have helped promote awareness of the condition in recent years.
Andy, who is approaching his 80th birthday, wrote his new book with assisted technology.
He recalled how his life was turned upside down when he was diagnosed with the terminal illness age 43.
"I was sitting right on top of the world. Married with a wife and six children, they were my joy and greatest treasures," Andy said.
"I had my own business and the world was mine."
He hopes his memoir will inspire as well as helping to raise funds for the Irish Motor Neurone Disease Association (IMNDA).