Concussion is defined as a complex pathophysiological process affecting the brain that is induced by traumatic biomechanical forces.

Sport and recreation-related concussions are conservatively estimated at 1.6 to 3.8 million cases each year in the United States alone. The wars in both Iraq and Afghanistan have had the distinction of producing the greatest number and percent of mild traumatic brain injuries (TBIs; concussion) that have ever been documented in a major war owing to roadside explosions.

Whether occurring from sports collisions or bombings, concussion can result in both short-term and long-term impairment of neurological function and the possibility of significant neuropathological changes.

A smaller percentage of cases can exhibit signs and symptoms referred to as postconcussive syndrome (PCS), which may be prolonged or permanent.

In sports-related concussion, most physical signs and symptoms such as nausea, visual disturbances, headache, and balance changes will resolve within 2 to 7 days. Longer- lasting complaints such as fatigability, poor concentration, behavior changes, sleep pattern changes, and mood alterations that last beyond this time frame are considered PCS.
Often, PCS will result in significant disruption of school, work, and other activities and in the need for further medical evaluation. The military has seen an increased incidence of depression and other symptoms often referred to as posttraumatic stress disorder in many of the soldiers who have suffered from mild TBIs.

PMID: 21916127

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