Concussion

Descriptive text is not available for this imageBASICS

DESCRIPTION

  • Concussion is a clinical syndrome of biomechanically induced alteration of brain function, typically affecting memory and orientation, which may involve loss of consciousness (LOC). Symptoms are transient and usually resolve within hours to days.
  • The term mild traumatic brain injury (mTBI) has been used as a synonym for concussion in the literature.
  • Concussion may be caused either by a direct blow to the head or a blow to the face, neck, or elsewhere on the body with an “impulsive” force transmitted to the head.
  • Concussion may result in pathologic changes, but the acute clinical symptoms largely reflect a functional rather than structural injury, and there is no evidence of intracranial injury (ICI) in imaging.
  • The symptoms of concussion typically resolve spontaneously over hours to days; however, postconcussive symptoms may be prolonged.

EPIDEMIOLOGY

  • Concussion can occur after any type of head trauma, but sports-related concussions are of particular interest.
  • It is difficult to establish the exact incidence of concussion because of variability in presentations and in particular because of underreporting of concussion and the lack of widespread surveillance in youth sports.
  • Vulnerable populations for concussions include children aged 0 to 4 years and adolescents, with males more commonly affected than females.
  • From 2005 to 2009, children made >2 million outpatient visits and almost 3 million emergency department (ED) visits for concussion.
  • The Centers for Disease Control and Prevention (CDC) estimates that approximately 3.8 million recreation- and sport-related concussions occur annually in the United States.
  • Although concussion is overall more common in boys, girls have higher rates of concussion than boys in similar sports (e.g., soccer).

RISK FACTORS

  • Risk of sports concussion depends on sex, sport, position, and history of prior concussion.
  • For boys, concussions are most likely in rugby, football, ice hockey, and lacrosse.
  • For girls, concussions are most likely in soccer, lacrosse, and field hockey.
  • There is an increased risk for repeated concussion in the first 10 days after an initial concussion.
  • Multiple concussions are a risk factor for chronic neurobehavioral impairment

GENERAL PREVENTION

  • Minimizing high-risk situations for concussions as well as enforcing strict guidelines on the management of a concussion may be the best chance to reduce concussions and their sequelae symptoms.
  • Helmet use is the single most important preventive measure for serious traumatic brain injury. However, helmets have not been consistently shown to prevent concussion.
  • Helmets are not effective at preventing movement of the brain within the skull.
  • The best prevention strategy is to educate parents, teachers, and the general public on signs and symptoms of concussion.
  • At preparticipation medical visits, providers should emphasize that reporting concussion immediately is essential.
  • Children with more than one concussion should be cleared by a physician before returning to activity.
  • Baseline neuropsychological testing (prior to concussion) is being performed by many school athletic departments via widely available computerized testing modules. Research is still needed regarding the optimum timing of this testing and whether baseline testing improves outcome.
ALERT

Retirement should be considered when any athlete who has sustained three concussions in an individual season, when an athlete has had postconcussive symptoms for >3 months, when recovery requires an increasing amount of time or when concussions occur with less forceful injury.

PATHOPHYSIOLOGY

  • Concussion occurs with rapid rotational acceleration of the brain.
  • With acceleration–deceleration, the brain experiences continued momentum after impact and strikes against bone. The temporal and frontal lobes are particularly prone to injury because of their location adjacent to irregular parts of the skull.
  • Depressed level of consciousness is thought to be the result of rotational stretch injury to the reticular activating system in the dorsal aspect of the brainstem.
  • Pathologic changes after concussion include alterations in neuronal depolarization and neurotransmitter release, impaired axonal function, lactic acid accumulation, and decreased cerebral blood flow/autoregulation and glucose metabolism.
  • Children may respond to brain trauma differently than adults due to developmental factors such as brain size, brain water content, myelination level, skull and suture geometry and elasticity, and differential skull to body proportions.

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