Overview - DEFINITION

Concussion is a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces. Several common features that incorporate clinical, pathological, and biomechanical constructs that may be used in defining the nature of a concussive injury include:

1. Concussion can occur from either a direct blow to the head or face or to the body with an “impulsive” force transmitted to the head.
2. Concussion typically results in rapid onset of symptoms that quickly resolve spontaneously.
3. Acute symptoms are largely a functional disturbance of the brain and not the manifestations of a structural injury. Therefore, most conventional neuroimaging, such as CT and MRI, is usually normal.
4. Resolution of symptoms typically follows a sequential course.
5. Concussion may involve loss of consciousness but most concussions (85%) do not. 

Concussion in Sport Group, (2016). Consensus statement on concussion in sport—the 5th international conference on concussion in sport held in Berlin, October 2016. British Journal of Sports Medicine.