How can I communicate with a non-verbal person who has suffered a tbi and cannot move ( to point or nod)?

I work for a 23 year old DD man. He suffered a SCA at age 14 which left him unable to speak or move. He can still laugh and is not brain dead, but cannot answer yes or no. Is there some device that would enable me to communicate with him and at least get a yes or no answer out of him?How can I communicate with a non-verbal person who has suffered a tbi and cannot move ( to point or nod)?
try to check on google...good luck