According to The Sun, his barrister Judith Benson said: "His isolation because of his deafness within the prison is increased in comparison to an ordinary prisoner.
"He is unable to watch TV or partake in any other media of that sort.
"His life essentially consists of a period of time in workshops where he is able to have minimal communication.
"Save for that, he has no means of communication or passing time."
Demian, who was branded "dangerous" by judges, moved to West London in 2004 and worked in a shop.
He will serve an extra three years on extended licence following his prison sentence.
At the Court of Appeal, judge Adele Williams said: "We are persuaded some reduction is appropriate."