A "concussion" is derived from the Latin concutere, meaning to shake violently. It is also often referred to as an MTBI (mild traumatic brain injury).
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.
Collision of brain and skull
The word "concussion" is derived from the Latin word "concutere", meaning to shake violently. It is also often referred to as an MTBI (mild traumatic brain injury).
Recent international consensus statements on concussion in sport (Vienna, 2001; Prague 2004, and Zurich 20081) all define a concussion as a "complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces."
In layperson's terms, a concussion occurs when a blow to the head, face, neck, or a blow elsewhere on the body that is transmitted to the head, trauma 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.
According to Dr. Robert Cantu, a concussion causes temporary metabolic changes in brain function, which one expert likens a concussion to a break in the local cables in a television network that results in lengthy re-routing of the call, so that when it finally gets through, it's delayed and full of static.
Five common features
Every concussion is different. Experts acknowledge that the science of concussion is evolving and therefore that management and return to play decisions "remain in the realm of clinical judgment on an individualized basis."1
All concussions, however, five common features1:
- Direct blow to head not required. A concussion may be caused by a direct blow to the head, face, neck, or elsewhere on the body with a force transmitted to the head.
- Rapid onset and gradual resolution of symptoms. A concussion typically results in the rapid onset of symptoms of impaired neurological function that, in most cases, gradually disappear spontaneously with rest, usually within a week to 10 days.
- Brain function disrupted. A concussion may result in neuropathological changes but the acute clinical symptoms largely reflect a functional disturbance in the barin rather than structural injury.
- Loss of consciousness not required. Concussions result in a graded set of clinical symptoms that may or may not involved loss of consciousness (LOC). Resolution of clincal and cognitive symptoms typically follow a sequential course, but in a small percentage of cases, post-concussive symptoms may be prolonged.
- Normal MRI/CAT scans. Concussion is typically associated with grossly normal structural neuroimaging studies. In other words, unlike other injuries, concussions are usually injuries no one sees and, contrary to popular belief, don't show up on most magnetic resonance imaging (MRI) exams or CT scans. A brain CT - or, where available, MR brain scan - should, however, be conducted if symptoms of a more serious brain injury are present.
1. Concussion Statement on Concussion in Sport: the 3rd International Conference on Concussion in Sport held in Zurich, November 2008, P. McCrory et. al, Br. J. Sports Med. 2009; 43; i76-i84.