Mild forms of brain injuries are often described as invisible because they do not appear on traditional medical scans. Using advanced MRI techniques, the authors of the Neurotrauma study were able to make the once-invisible – visible. Quite notably, the study found that the brains of athletes who had a history of concussion had visible decreases in brain volume and blood flow as compared to those athletes who had not experienced concussion.
http://otlablog.com/concussion