Impact and the Brain
From: Scientific American Mind - 12/2008
By: Richard J. Roberts

Mild traumatic brain injury represents a silent but brutal plague among
combat veterans and a hidden threat to the health of civilians 

As a combat engineer in Iraq, Jeremy was supposed to find roadside bombs.
They found him instead. Within 72 hours of each other, two improvised
explosive devices (IEDs) went off within 15 feet of this father in his late
20s. The first set of blast waves, a moving wall of highly compressed air
that emanates from an explosion, knocked him out briefly. The second left him
dazed for about 30 minutes and produced ringing in his ears that disappeared
within a week. These detonations did not visibly injure Jeremy (not his real
name) - but he was never the same. 

Read the entire article at:
http://www.sciam.com/article.cfm?id=impact-and-the-brain