“I’ve survived with having a great memory all my life. The next week... I lost my voice. I couldn’t get a word out and it was absolutely terrifying.
“Everything was going through my mind – is my memory going to be back? Am I ever going to speak again?
Ferguson said he worked with a speech therapist and his voice returned after 10 days.
“The speech therapist came and told me to write down all the members of my family, of my football team... She asked me questions about animals, fish, birds. Eventually after 10 days my voice came back,” he said.
“I realised, having gone through all that, my memory was fine.”
Ferguson was United manager from 1986 to 2013, winning the Champions League twice, the Premier League 13 times and five FA Cups.
He was knighted in 1999, the year United won the treble of Champions League, Premier League and FA Cup.