WorriedMom,
I recommend reading/studying "Healing ADD" by Daniel G. Amen, M.D. I have my copy in front of me.
In chapter 11, "Head Trauma - Induced ADD," Dr. Amen discusses the ADHD like symptoms that childhood head injuries can cause. Unexplainable headaches often accompany
Head Trauma - Induced ADD according to Dr. Amen.
The ADHD like symptoms always occur after the head trauma. However, if the injury occurred at birth or at a very young age, head trauma ADHD can become indistinguishable from ADHD the named disorder. And, according to Dr. Amen, if the injury affected the temple regions, can cause mood instability.
I highly recommend the book and you might consider getting your son an appointment at one of Amen's clinics.
Bob
PS Welcome to the board.