Not so sure it changes personality, but it does cause some types of changes. As I began to lose my hearing, I missed out on lots of things people were talking about. My wife began to think I was ignoring her with some selective hearing, and I think it made her frustrated. I just kept telling her I could not hear her, and then I started getting frustrated. As my hearing got worse, I spent a lot of energy trying to hear conversations a little better. I'm not sure how to explain this, but it would be similar to a person that removes their glasses, and then tries to read the paper...you keep squinting your eyes trying to read, and it takes some real effort to do this. It makes you tired.
Age might be the difference. I am 62, and my body is beginning to slowly fall apart...and I accept these changes as just part of getting older...my hair is gray, I wear glasses, had a stroke, heart surgery so I won't have another stroke, cataract surgery, AN surgery...and I am not frustrated by any of this. It is just part of getting older. However, if I was 22 or 32 or 42, I might be totally shocked that something like a brain tumor happened to me, I might get depressed. Lose my hearing, lose my balance, and my face won't work...this is happening to me???!!
This is a BIG deal. Get him to visit this site and communicate with some of us who hang out here. Lots of information here, lots of friends. This site can help him put this experience in its place.
James