The Welsh-born 74-year-old’s spokesman verified that he is not able to give interviews any more following the heartbreaking diagnosis.
The report comes as it is announce that BAFTA Cymru have given him a gala award for his outstanding contribution to film and television.
The spokesman said: “Terry has been distinguished with primary progressive aphasia, a variant of frontotemporal dementia.
“This affliction affects his ability to communicate and he is no longer able to give interviews.
“Terry is proud and honoured to be recognised in this way and is looking brazen to the celebrations.”
Terry, a popular comedian, also directed Life Of Brian and Monty Pyton’s The Gist Of Life. As well as that, he co-directed Monty Python and the Holy Grail with Terry Gilliam.
Construction artist Sian Grigg has also been recognised by Bafta Cyrmu in advance of their awards bash on October 2.
Hannah Raybould, director of Bafta Cymru, said: “The Bafta Cymru cabinet recognises Sian’s talents and her huge contribution to such an array of veils including Titanic, The Aviator, for which she won the Bafta for make-up and hair in 2005, and varied recently The Revenant for which she also received a Bafta nomination.
“We are also bloody much looking forward to celebrating the work of Terry Jones during the service with a look back at his work from 1969 to the present day.”
Terry is also an expert writer and historian, and has written several works on medieval history and the yesterday of numeral systems.
Furthermore, he is a member of the UK Poetry Society and has performed as a musician with The Carnival Belt.