McCourt, whose book was made into a hit movie, has been battling melanoma skin cancer in a New York hospice, but his condition took a turn for the worse when he contracted the deadly brain disease.
And the 78 year old is not expected to recover from the illness, according to his brother, veteran actor Malachy McCourt.
He says, "We don't expect him to live very long. He got meningitis and that screwed up the whole thing. (Until then) he was doing okay, speaking and lecturing and appearing and signing and doing all the usual stuff.
"He was one of the unfortunate ones. Only three to five per cent of people who have melanoma get this form of meningitis.
"He's still conscious, but his hearing has gone and his eyesight is going. He's speaking less.".