Concussions and their consequences: current diagnosis, management and prevention (original) (raw)

2013, Canadian Medical Association Journal

C oncussion is the most common type of mild traumatic brain injury and can have serious consequences. Not just confined to high-profile athletes, concussions are frequent in all age groups and in a variety of settings, such as the work environment, motor vehicle crashes, sports and recreation, and falls at home among older people. Concussion is defined by the International Consensus Conference on Concussion in Sports as "a complex pathophysiological process affecting the brain, induced by biomechanical forces." 1 Concussion is the preferred term be cause of its familiarity to the public. Since 2000, international expert panels have clari fied the definition and modified the management of concussion; these changes have affected recommendations for return to work, school and sport for those experiencing a concussion. 1,2 The importance of accurate and timely recognition and management stems from the consequences of misdiagnosis or faulty management that can lead to major disability or death, in both the short and long term. Second-impact syndrome occurs when a concussed person, especially a younger person, returns to play before complete recovery and sustains a second brain injury. However, malignant brain swelling can occur even without a second injury. 3 Also, repeated concussions may cause delayed posttraumatic brain degeneration, leading to dementia and movement disorders similar to Alzheimer and Parkinson diseases. 4 Thus, it is important for practitioners to know the current principles of recognition and management of concussions, including the physical, cognitive and emotional effects and the guidelines for return to play, work or school. Mechanism The exact mechanism of concussion is unknown. Axon tearing occurs in more severe brain injuries, but proof is lacking for this mechanism in concussion. It is more likely that concussion is due to rotational acceleration of the brain (jiggling of the brain) 5 that produces a disordered metabolic cascade or biochemical injury such as altered metabolism of glucose or derangement of adenine nucleotides. 6 It is still uncertain where in the brain concussion occurs, or the exact origin of the symptoms of acute concussion. It is now apparent that direct impact to the head is not required: concussion can occur with a blow to the chest, for example, that causes a whiplash effect on the brain. Whiplash of the neck and concussion frequently co-exist. 7 Risk factors The young brain is more susceptible to concussion than the adult brain and may require more time to recover. 8 Also, it is now known that, after a concussion, there is greater susceptibility to sustaining another concussion and that subsequent concussions occur with less force and take longer to resolve. 9 New information indicates that females may be more susceptible to concussion than males 10 and that there may be a genetic factor underlying susceptibility to concussion. 11