My 1 1/2 Year Old Cat Recently Was Diagnosed With Supposed Head Trauma, From What, We Don't Know. He Has No Physical Signs Of Any Kind Of Accident. What Could This Be?

My cat has very little function. He needs assistance in eating, drinking etc. He is like a combination of amnesia and a labotomy. We hope in time he will regain full function and have a happy life. Right now when i get his attention you can see the loving cat that he was, but then he goes back to his own world. What can i do to try to get him to eat and drink on his own and also what other kinds of therapy can i do for him.