In my travels just now I found an interesting article about headaches associated with Post Concussion Syndrome.

Just thought I'd add on there in case it's of help to someone...

http://www.hacoop.org/professionals_5_1.html
Chronic Post-Traumatic Headache (2003)

Thomas N. Ward, MD and Morris Levin, MD
Co-Directors, Dartmouth Headache Center
Lebanon, New Hampshire