I think that one of the most important choices in finding a Psychologist in your situation Sam would be for your parents to find someone who is knowledgeable and familiar with treating patients who have psychological symptoms of Post Concussion Syndrome.

There are numerous associations set up for TBI.

e.g. Someone like the Brain Injury Association in your local area should be able to help.

http://www.biausa.org/state-affiliates.htm
Brain Injury Assoc. - Find your State.