The Prevalence of Undiagnosed Concussions in Athletes

William P. Meehan, III, MD; Rebekah C. Mannix, MD, MPH; Michael J. O'Brien, MD; Michael W. Collins, PhD


Clin J Sport Med. 2013;23(5):339-342. 

In This Article

Materials and Methods


We conducted a cross-sectional study of patients seen in 2 sport concussion clinics, the Sports Concussion Clinic at Children's Hospital Boston and the University of Pittsburgh Medical Center Sports Medicine Concussion Program, Bethel Park location. All patients seen between October 1, 2009, and September 30, 2010, were considered for enrollment. We included all sport-related concussions. In addition, patients with injury mechanisms and forces similar to those observed in sports, such as falling from a standing position or fistfighting, were also included. We excluded patients with more severe injury mechanisms and forces, such as motor vehicle accidents and falls from above ground level.

Definition of Concussion

We used the definition of concussion proposed by the international consensus on concussion in sport.[5] Thus, athletes experiencing a traumatic acceleration of the brain followed by the onset of symptoms of concussion, signs of concussion, or decreases in neurocognitive function were diagnosed as a concussion.

Definition of Undiagnosed Concussion

Standardized intake and follow-up visit forms were used at each location. Patients entered demographic information (eg, date of birth and gender) and clinical data [eg, day of injury, sport played at time of injury, and score on the Post Concussion Symptom Scale (PCSS)]. In addition, each patient was given a copy of the PCSS included in the consensus statement on concussion in sport[5] and asked to answer the following question: "Have you ever sustained a blow to the head which was not diagnosed as a concussion but was followed by one or more of the signs and symptoms listed in the Post Concussion Symptom Scale?" Patients answering "yes" to this question were defined as having a previously undiagnosed concussion.

The PCSS is a symptom inventory containing a total of 22 symptoms that athletes rank on a scale from 0, when an athlete is not experiencing a given symptom, to 6, when the athlete describes the symptom as "severe." The PCSS is part of the Sport Concussion Assessment Tool 2, which was proposed by the Third International Consensus on concussion in sport. The total score on the PCSS is the sum of the athlete's severity score (0-6) for each of the 22 symptoms. Thus, the maximum possible score on the PCSS is 132 (6 × 22).

A history of concussions is associated with an increased likelihood of loss of consciousness (LOC), increased scores on symptom inventories, and increased symptom duration with a recurrent injury.[6–8] Thus, we compared the rates of LOC, the mean symptom scores, and duration of concussion symptoms between athletes with previously undiagnosed concussions, and those without previously undiagnosed concussions as a way of validating the self-reported history of undiagnosed concussions.

The mean values for continuous variables were compared between the 2 groups using Student t test; proportions between the 2 groups were compared using [chi]2 test. All analyses were done with PASW Statistics 18.0 (SPSS, Inc, Chicago, Illinois). This study was approved by the institutional review board of Boston Children's Hospital.