A "concussion" is the historical term representing low-velocity injuries that cause brain "shaking." (1)(the word, in fact, is derived from the Latin concutere, meaning to shake violently) It is a subset of mTBI (mild traumatic brain injury) (2), a term with which it is often used interchangeably, especially in the United States (1).
In layperson's terms, a concussion results from trauma (usally but not always a blow to the head) which causes the brain - a jellylike structure which is normally protected from collisions with the skull by a tough, fluid-filled membrane - to collide with the skull.
A concussion causes temporary metabolic changes in brain function (3) which one expert likens a concussion to a break in the local cables in a phone network that results in lengthy re-routing of the call, so that when it finally gets through, it's delayed and full of static.
Four common features
While no two concussions are exactly the same, a concussion is defined under the most recent international consensus statement on concussion in sport (1) as follows:
Concussion is a brain injury and is defined as a complex pathophysiological process affecting the brain, induced by biomechanical forces. Several common features that incorporate clinical, pathologic and biomechanical injury constructs that may be utilized in defining the nature of a concussion head injury include:
1. Direct blow to head not required. A concussion may be caused by either by a direct blow to the head, face, neck, or elsewhere on the body with a force transmitted to the head.
2. Rapid onset and gradual resolution of symptoms. A concussion typically results in the rapid onset of short-lived impairment of neurological functions that resolve spontaneously. However, in some cases, symptoms and signs may evolve of a number of minutes to hours.
4. Loss of consciousness not required. Concussion results in clinical symptoms that may or may not involve loss of consciousness. Resolution of the clinical and cognitive symptoms typically follow a sequential course. However, it is important to note that in some cases symptoms may be prolonged.
1. McCrory P, et al. Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012. Br J Sports Med 2013;47:250-258.
2. Dematteo CA, Hanna SE, Mahoney WJ. et al. My child doesn't have a brain injury, he only has a concussion. Pediatrics 2010;125(2):327-334.
3. Giza CC, Hovda DA, The Neurometabolic Cascade of Concussion. J. Ath Train 2001;36(3):228-235.
Posted March 19, 2013