Pat,
I am sorry to hear of his condition. I understand your pain. My dog was injured with significant brain trauma. She was fine(really I placed at a big trial less than 3 weeks from the accident) just after the accident but 6 months later. She started missing little things. So little that my husband who also runs dogs could not even see. 1 year from the accident she was still trying and he could see when she missed flanks. 1 1/2 years from the accident I had her BAER tested and they said she was at that point 95% deaf. I was not ready to give her up yet she was my first dog I had trained to the Open and probably the best dog I have owned to this day.One day she went out the drive way and It took me 45 minutes of frantically calling and serching before I found her. I knew at that point she needed a more controlled environment. I hate to think if she had gone the other way she would have been out on the highway.
I found it hard to explain to my local vet that she just was not the same. He checked everything from Lymes to hips and all between. I keep complaining that it was like she didn't even know when she had screwed up. I even took her to a large teaching hospital 6 hours away. They to did not understand. I kept saying she is just not the same. Her energy is good and attitude was good but she had not connection to my commands and seemed confused. When we finally diagnosed the problem it was a relief. I guess there is something to that. At least you have your answer.
Best of luck