Worried_mom and others,
The notebook or journal is great. Take it to doctor's appointments to take notes, too. If you watch the eyes, you will begin to see when there are struggles. My wife can read me like a book by watching my eyes when I am struggling or starting to struggle.
It would be worthwhile to ask your injured person/son/husband to try to be open about any symptoms they notice. Let them know that this is not so you can try to fix it or such but rather so you can note it and try to understand what they are going through. Let them know that you don't take this as complaining or wining.
The TBI Survival Guide at
www.tbiguide.com does a good job of explaining the symptoms. You could even read through parts of it with them. You'll get, " Oh yeh, I have that all the time" or "I feel like that when too many people are talking at once."
Understanding what is happening is the first step toward helping them recover.