Some concussions are more severe than others.
a mighty tremor followed by minor concussions
Medics steadies trays of instruments against the Bomb concussions
The special M.R.I. technique, known as diffusion tensor imaging, is also being studied to help improve the diagnosis of concussions.
Simple concussions cause short losses of consciousness. Coma from lack of oxygen may last several weeks and is often fatal.
By the Pentagon's own admission, many soldiers who likely suffered this invisible form of TBI were never screened for concussions prior to 2009-2010.
