It's all in their heads

"A concussion is more a mild form of traumatic brain injury in which the brain is exposed to abnormal forces that result in transient neurological dysfunction," Ellis says. "But ‘mild traumatic brain injury’ is a bit of a misnomer."

Source/more:

http://www.winnipegfreepress.com/arts-and-life/life/health/its-all-in-their-heads-390878351.html

Headaches After Traumatic Brain Injury

Headache is one of the most common symptoms after traumatic brain injury (often called post-traumatic headache). Over 30% of people report having headaches which continue long after injury.

Source/more:

http://www.msktc.org/tbi/factsheets/Headaches-After-Traumatic-Brain-Injury