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Consensus Statement on Concussion in Sport: the 4th International Conference on Concussion in Sport - Zurich, November 2012

Concussion Evaluation and Management Involves Many Factors

Presence May Signal More Severe Injury, Increased Risk of Poor Outcome


Evaluation and management of concussion involves many factors, some of which may predict the potential for prolonged or persistent post-concussion symptoms and long-term health effects. 

The current international consensus of concussion experts ("Zurich consensus statement") (1) is that a range of "'modifying' factors may influence the investigation and management of concussion, and, in some cases, may predict the potential for prolonged or persistent symptoms, and in others suggest consideration be given to retirement from contact or collision sports: 

 Factors              Modifier                                                                                                               

Number (6)

Duration (greater than 10 days)

Severity (7)


Prolonged loss of consciousness (more than 1 minute duration)

Amnesia (Note that amnesia was not found in two 2013 studies (6,7) to be predictive of longer recovery, adding to an already muddled picture as to the role amnesia plays in predicting concussion recovery)

Sequelae Concussive convulsions (Note: it is puzzling that impact seizures are still listed as a modifying factor, as a study published simultaneously with the Zurich consensus statement (9) catagorically states that "the literature does not suppport the inclusion of impact seizures as a concussion modifer."

Frequency - repeated concussions over time (as discussed in the literature review accompanying the Zurich statement (9) @ Table 2, citing studies @ notes 31,103, 34, 17, and 12, "in general, athletes with a previous history of concussion are more likely to present a longer duration of symptoms and are withdrawn from competition for longer following their injury." While multiple concussion history was not found to be predictive of concussion symptoms lasting more than 28 days in one 2013 study (7), another 2013 study(14) found that concussion symptoms lasted twice as long for patients with a history of previous concussion as those without such a history (24 versus 12 days); that the median symptom duration for those with a multiple concussion history and who had sustained a concussion within the past year was 2 and 1/2 times longer (28 days) and nearly three times (33 days) longer respectively, compared with patients without such risk factors.

Timing - injuries close together in time (14)

"Recency" - recent concussion or traumatic brain injury (TBI)

[Note: timing and recency continue to be included in the list of modifying factors despite the finding in the accompanying literature review (9) that there is "limited evidence to suggest that the timing or 'recency' makes any difference to timeframe of recovery following a concussion."  A subsequent 2013 study (14)however,  suggests that children and adolescents who have sustained a single concussion within the past year are at even greater risk of prolonged symptoms.

Threshold Repeated concussions occurring with progressively less impact force or slower recovery after each successive concussion (Note, once again, the literature review accompanying the Zurich statement (9) concludes that the evidence to suggest longer timeframes of recovery for each subsequent concussion is "limited.")
Age Children and adolescents (less than 18 years old). "Recovery from concussion in children generally takes longer than that in adults. This is evident in time taken for symptom resolution, as well as neurocognitive recovery." (9) (Note, however, that two 2013 studies (6,7) did not find age to be predictive of symptoms lasting more than a week or more than 28 days or more than 28 days, respectively.) Note: delayed onset of symptoms is more common among younger athletes.
Co- and pre-morbidities (pre-existing medical conditions) Migraine (11,12), depression or other mental health disorders (11,12), attention deficit hyperactivity disorder (ADHD)(13), learning disabilities, sleep disorders.
Medication Psychoactive drugs, anticoagulants
Behavior Dangerous/more aggressive style of play (may be one reason athletes suffer recurrent concussions (5))
Sport High risk activity, contact and collision sport, high competitive level