With the recent congressional hearings on the NFL’s handling of brain injured players, the return of soldiers from the Iraq and Afghanistan wars who have suffered a traumatic brain injury, and the start of high school and college football just around the corner, discussion of concussion and head injury seems to be a common place in the media today. Indeed, the identification and management of concussion has become a growing public health issue. Considered to be the fastest-growing sub-discipline in neuropsychology, concussion management poses unique challenges and opportunities for those working with school-aged children.
Definition and Demographics
A concussion is a mild traumatic brain injury (TBI) caused by direct or indirect impact to the head. The American Academy of Neurology (1997) defines concussion as any alteration of mental status due to a biomechanical force affecting the brain with or without loss of consciousness.
Sport and recreational activities are the third-leading cause of TBI for children and adolescents. The U.S. Centers for Disease Control and Prevention (CDC) estimates that 300,000 sports-related traumatic brain injuries, most of which can be classified as concussion, occur annually in the United States (CDC, 1997). Team and contact sports such as football and ice hockey have the highest incidence of concussion, followed by soccer, wrestling, basketball, field hockey, baseball, softball, and volleyball (Koh et al., 2003), but concussion can also occur in individual sports such as gymnastics or diving.
The risk of concussion is highest in the 15- to 19-year-old age group; in addition, males are at higher risk than females (CDC, 2010).
Symptoms and Mechanisms
Concussion symptoms can include immediate memory disturbance, confusion, clumsiness, dizziness, and vomiting. The majority of children will make a complete recovery from a single concussion but it is important to remember that recovery can take days, weeks, and even months and that a number of cognitive and physical symptoms are possible. These post-concussive neurobehavioral symptoms are typically divided into three domains — somatic, cognitive, and emotional/behavioral — and can include any combination of symptoms.
Like other TBIs, a concussion involves rotational acceleration/deceleration forces to the brain that can stress and tear axons and the vasculature, causing diffuse injury, cell death, and intracranial bleeding. In addition to understanding these biomechanical forces, considerable progress has been made in understanding the brain's chemical response to concussion through animal models. Whereas the healthy brain is constantly working to achieve chemical equilibrium, concussion can cause a "cascade" of significant metabolic disturbances in the brain including decreased cerebral blood flow, increased production of glucose and glutamate, and abnormal cellular ionic fluxes that can take minutes, hours, or days to return to equilibrium (Giza & Hovda, 2001).
Effects of Multiple Concussions
Not only is metabolic dysfunction thought to underlie concussion symptoms, but some researchers believe that until equilibrium is achieved again, the brain may be more vulnerable to a second injury. This second injury, regardless of severity, can produce catastrophic outcomes from severe neurological dysfunction to death. The term "second-impact syndrome" refers to an individual who sustains an initial head injury and then sustains a second head injury before the symptoms associated with the first injury have resolved (Cantu, 1998). The second injury can be minor (e.g., a blow to the chest that jerks the head) but potentially can be fatal for the athlete [e.g., 17 deaths in individuals under age 30 related to second-impact syndrome were reported between 1984 and 1995 across a range of contact sports including football, hockey, and boxing, (Cantu & Voy, 1995)].
The concussion literature includes a long-held assumption that multiple concussions are predictive of a lower threshold for subsequent injury and a worse outcome afterward (Collins et al., 2002). Yet the data are equivocal: Studies (Collins et al., 1999; Collins et al., 2002) have shown that multiple concussions are associated with poorer performance on neurological tests, prolonged learning difficulties, and increased vulnerability to subsequent concussion than in individuals with a single or no concussion; other studies (Iverson et al., 2006; Macciocchi et al., 2001) have shown no significant differences on cognitive testing or in on-field presentation of symptoms between athletes with one or two concussions.
The Kennard principle (Kennard, 1936) states that due to neuroplasticity, a young brain is more adaptive and protective against damage than an older, adult brain. Recent studies (e.g., Levin et al., 2001), however, suggest that the developing brain is actually more vulnerable to the effects of widespread damage associated with TBI. To date only one study has directly compared concussion recovery rates by age (high school vs. college athletes); although the college sample had a greater prior incidence of concussion in that study, the high school students took longer to recover (Field et al., 2003). More research is needed to replicate and extend this finding to younger developmental samples, but there are neurobiological (e.g., cerebral blood volume, level of myelination) and biomechanical (e.g., less well-developed neck and shoulder musculature) differences between children and adults that may make young children more vulnerable to the effects of concussion and account for more protracted recovery rates (Lovell et al., 2004; McCrory et al., 2004). The age of the athlete who has experienced a concussion, therefore, may affect outcome and clinical decision-making regarding return to play and academic life. Efforts are underway to obtain incidence data and to conduct empirical studies examining recovery rates and long-term outcomes in elementary and middle-school populations.
Duff, M. (2009, July 14). Management of Sports-Related Concussion in Children and Adolescents. The ASHA Leader. Used with permission. www.asha.org.