October 24, 2014

SAN DIEGO — Up to 14.5% of adolescent athletes who play sports might experience undiagnosed concussions, according to the results of a new study.

“The burden in sports concussions may be greater than we know about from the literature, and there may be undiagnosed concussions or repeat traumatic brain injuries that we haven’t captured yet,” Mackenzie Herzog, MPH, research coordinator at Children’s Healthcare of Atlanta, told Medscape Medical News.

Herzog presented the research here at the American Academy of Pediatrics (AAP) 2014 National Conference and Exhibition.

The retrospective study looked at local athletes aged 12 to 18 years who participated in organized sports and had been under the care of the sports medicine staff at Children’s Healthcare. The athletes had not been diagnosed with or reported to have suffered a concussion, but all of them had undergone two baseline tests using the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) assessment tool.

The researchers compared neurocognitive performance of the athletes using ImPACT scores. ImPACT measures verbal memory, visual memory, reaction time, and processing speed. It also evaluates 22 common concussion symptoms. Athletes were tested initially before participating in organized sports, and underwent a second test 8 months to 2 years after the first. The researchers excluded teenagers with impulse control composite scores higher than 30.

To compensate for potential normal variation in test scores, the researchers used the Reliable Change Index to determine whether a change was statistically significant. Any statistically significant difference between performances on the test was considered to indicate a potentially undiagnosed concussion.

The 290 study participants played sports that included football, boys’ lacrosse, boys’ soccer, girls’ soccer, and wrestling. Of these, 42 (14.5%) had test results suggesting a cognitive function decline that would be consistent with an undiagnosed concussion. Thirty-five declined on one composite score or symptom scale, five declined on two scores or scales, two declined on three, and one participant declined on all five.

In contrast, 83 athletes (28.6%) showed neurocognitive improvement on the second test.

Football players were the only group to have a significant increase in the risk for a decline in score.

Table. Neurocognitive Decline by Sport

Sport Evidence of Neurocognitive Decline Risk Ratio (95% Confidence Interval)
Football (n = 126) 25 (19.8%) 1.84 (1.11 – 3.06)
Wrestling (n = 8) 2 (25.0%) 1.03 (0.95 – 1.12)
Girls’ soccer (n = 36) 4 (11.1%) 0.97 (0.85 – 1.10)
Boys’ soccer (n = 38) 2 (5.3%) 0.89 (0.81 – 0.98)
Boys’ lacrosse (n = 62) 3 (4.8%) 0.83 (0.73 – 0.94)


“There may be a difference between sports, and that’s something that needs to be looked at further,” said Herzog.

The research drew some criticism. One audience member suggested that the use of ImPACT scores in this study was inappropriate.

Herzog conceded that the test captures neurocognitive symptoms, not clinical symptoms. “But I think it’s commonly used in concussion testing, which makes it potentially useful for screening athletes,” she said.

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There was also concern that the group compared just two test performances. There might be natural variation in performance on the ImPACT test, explained Stephen Rice, MD, director of the Jersey Shore Sports Medicine and Concussion Center in Neptune, who attended the session.

“I think that’s one of the dangers here, because you have variability at both ends. There are concerns about how accurate it is to say there are undiagnosed concussions in that circumstance, based on that difference, when it could be just the variability of the test,” he told Medscape Medical News.

Herzog countered that the use of the Reliable Change Index is designed to account for such variation. “We don’t mean this to be a definitive study, but I think it’s something we need to look into further to see if there’s a relationship between sports and undiagnosed concussions,” she said.

The researchers hope to do a prospective study next, enrolling individuals in contact and noncontact sports and including a nonathlete control group.

Mackenzie Herzog and Dr Rice have disclosed no relevant financial relationships.

American Academy of Pediatrics (AAP) 2014 National Conference and Exhibition: Abstract 26610. Presented October 11, 2014.


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