title: Cerebral concussion in athletes: evaluation and neuropsychological testing.
abstract: OBJECTIVE
  To conduct a topic review of studies related to cerebral concussion in athletes, as an aid to improving decision-making and outcomes.
  
  
  METHODS
  We review the literature to provide an historical perspective on the incidence and definition of and the management guidelines for mild traumatic brain injury in sports. In addition, metabolic changes resulting from cerebral concussion and the second-impact syndrome are reviewed, to provide additional principles for decision-making. Neuropsychological testing, as it applies to athletes, is discussed in detail, to delineate baseline assessments, the characteristics of the neuropsychological evaluation, the neuropsychological tests used, and the methods for in-season identification of cerebral concussion. Future directions in the management of concussions are presented.
  
  
  RESULTS
  The incidence of cerebral concussions has been reduced from approximately 19 per 100 participants in football per season to approximately 4 per 100, i.e., 40,000 to 50,000 concussions per year in football alone. The most commonly used definitions of concussion are those proposed by Cantu and the American Academy of Neurology. Each has associated management guidelines. Concussion or loss of consciousness occurs when the extracellular potassium concentration increases beyond the upper normal limit of approximately 4 to 5 mmol/L, to levels of 20 to 50 mmol/L, inhibiting the action potential and leading to loss of consciousness. This phenomenon helps to explain the delayed effects of symptoms after trauma.
  
  
  CONCLUSIONS
  Neuropsychological testing seems to be an effective way to obtain useful data on the short-term and long-term effects of mild traumatic brain injury. Moreover, knowledge of the various definitions and management strategies, as well as the utility of neuropsychological testing, is essential for those involved in decision-making with athletes with mild traumatic brain injuries.
authors.affiliation: Department of Neurosurgery, University of Pittsburgh Medical Center, Pennsylvania 15213, USA. maroonjc@msx.upmc.edu
authors.forename: J C
authors.initials: JC
authors.lastname: Maroon
authors.forename: M R
authors.initials: MR
authors.lastname: Lovell
authors.forename: J
authors.initials: J
authors.lastname: Norwig
authors.forename: K
authors.initials: K
authors.lastname: Podell
authors.forename: J W
authors.initials: JW
authors.lastname: Powell
authors.forename: R
authors.initials: R
authors.lastname: Hartl
mesh_terms: D001265:Athletic Injuries / Q000175:diagnosis* / Q000453:epidemiology / Q000628:therapy; D001924:Brain Concussion / Q000175:diagnosis* / Q000453:epidemiology / Q000628:therapy; D003430:Cross-Sectional Studies; D005538:Football / Q000293:injuries; D006688:Hockey / Q000293:injuries; D006801:Humans; D015994:Incidence; D009483:Neuropsychological Tests; D017410:Practice Guidelines as Topic