I too underwent 2 of these tests - the first on my dime concluded concussion and the second by the 3rd party insurance. a few months later. The 2nd report went on to say well if you did suffer a head injury it should be completely resolved, therefore since you still have symptoms, then something other than the injury is the cause. I too was given the pre-interview that dissected my childhood. I am 50 so I was honest but I do feel somewhat that that is trickery used to point to possible other causes... In any case I still showed some deficits.
Mark is very helpful in pointing out things that most doctors do not have the training or expertise in. I hope you find a doc who has a better understanding of the brain. My thoughts are if you were not in any psycho therapy or having other mental treatments prior to your accident or within the last several years from the time of the accident, then your atty should be able to keep those from gaining any traction. I do know now that the insurance companies on either side will do whatever they can to blame something else.
It is sad, but because of profits and fraud they are very defensive unless you have a blood and guts injury. They even try to deny orthopedic injuries by saying they were pre-existing. I wish you well. I would like to keep in touch as we are in somewhat similar boats and sharing helps everyone going through this maze.

Also do you have documentation from and ER or doc stating you had a concussion or head injury. Most docs seem to think you had to be unconsious before any brain trauma can occur (in concussion injuries).

There is enough information out there that substantiates a whiplash trauma can be actually worse than striking your head directly.

What was the nature of your head injury. Did you strike your head, whiplash, unconscious etc...?