"Terry has been diagnosed with Primary Progressive Aphasia, a variant of Frontotemporal Dementia," a representative for Jones said in a statement released through BAFTA. "This illness affects his ability to communicate and he is no longer able to give interviews."
The statement came along with news that the academy will present its Special Award for Outstanding Contribution to Film and Television to Jones.
Though famous for Python, the 74-year-old has also written and directed drama films, presented documentaries, composed operas, written short stories and published poems.
Primary progressive aphasia is described by the National Aphasia Association as a rare neurological syndrome that affects a person's ability to communicate. The syndrome is often a result of strokes or head injuries and can occur in other neurological disorders, including brain tumors and Alzheimer's disease.
Symptoms often begin about age 60 and gradually worsen over time. People with primary progressive aphasia can eventually lose their ability to understand written or spoken language.
Most people with the condition are between 40 and 80, though men are affected twice as often as women, the association said. Although some patients may benefit from speech therapy, no medicines exist to treat the condition.
"Of course this has been no secret to us for some years but he did manage to make O2!" his Monty Python co-star Eric Idle said Friday on Twitter, referring to the group's reunion performances in London in 2014.
Formed in 1969, Monty Python also included Terry Gilliam, John Cleese, Michael Palin and Graham Chapman, who died in 1989. Jones directed some of the troupe's best-known films, including "The Meaning of Life," "Life of Brian" and "Monty Python and the Holy Grail."
"We are very much looking forward to celebrating the work of Terry Jones during the ceremony with a look back at his work from 1969 to the present day," said Hannah Raybould, director of BAFTA Cymru.
Jones' representative said of the award, "Terry is proud and honoured to be recognised in this way and is looking forward to the celebrations."