Sports Medicine Research: In the Lab & In the Field: With Concussions, It’s Not Always the Hit You See (Sports Med Res)
Monday, April 15, 2013

With Concussions, It’s Not Always the Hit You See

Timing of concussion diagnosis is related to head impact exposure prior to injury

Beckwith J.G., Greenwald R.M., Chu J.J., Crisco J.J., Rowson S., Duma S.R., Broglio S.P., McCallister T.W., Guskiewicz K.M., Mihalik J.P., Anderson S., Schnebel B., Brolinson G., Collins M.W. Medicine & Science in Sports & Exercise. 2013; 45:747-754

Take Home Message: Delayed-concussion diagnoses are preceded by a higher number of impacts where as concussion diagnosed at the time of injury are associated with higher kinematic measures.

Diagnosis of a concussion is in part decided by whether an athlete reports one or more concussive signs or symptoms; however, it is not uncommon for athletes to report these signs and symptoms day(s) after an injury. The delayed reporting may be attributable to athletes not wanting to stop playing, athletes not recognizing that they were injured, the symptoms developing later, and/or perhaps different types of head impacts (e.g., locations of impact, frequency of impacts, force of impact). Understanding which factors are associated with delayed reporting may help us better understand concussions and recognize athletes who may report delayed symptoms. Therefore, researchers examined whether impacts associated with immediate diagnosis of concussion would have different characteristics (e.g., location, frequency, force) than impacts associated with delayed diagnosis. Football players from 8 colleges and 6 high schools wore instrumented [Head Impact Telemetry (HIT) system] helmets to record measures of head impact exposure (i.e., frequency, location, and kinematic response of head impacts) during a 6-year period. Ninety-five football athletes sustained 105 cases of diagnosed concussions (eight players sustained 2 concussions and 1 player sustained 3 concussions). The authors defined immediate concussion diagnosis as a concussion with 1 single identifiable head impact that lead to signs and symptoms and the athletes was immediately removed without reentry. Delayed diagnosis was defined as a diagnosed concussion, where the player was not immediately withdrawn and continued to play, and a clinician made a diagnosis later in the day or within the following days. The authors classified 45 athletes with an immediate diagnosis and 60 athletes with a delayed diagnosis. Both groups had similar durations of signs and symptoms (~ 6 days). Furthermore, most of the athletes sustained head impacts associated with a concussion to the front of the head (46%) or the top of the head 25%) and this was not different between groups. The authors found that athletes with an immediate diagnosis had higher impact measures, with the exception of peak rotational acceleration, compared to athletes with a delayed diagnosis. In contrast, athletes with a delayed diagnosis sustained twice as many impacts during the 7 days prior to the injury as well as almost 40% more impacts on the day of the injury compared to athletes with an immediate diagnose.

This study is important because it suggests that athletes who report delayed symptoms may be exposed to repetitive head impacts rather than the one big impact we’re accustomed to thinking about with concussions. Researchers have tried to determine a force threshold for diagnosing a concussion, but this study further complicates this since a concussion can result from not only from a single impact but from mild repetitive impacts. In addition, concussions can be difficult to diagnose due to the reliance of self-reported signs and symptoms. It was interesting to note that no matter when the athletes were diagnosed with the concussion it did not affect their recovery time, which suggests that multiple mild head impacts are just as severe as a single impact. Medical personal should be aware of those athletes with repeated impacts since this mechanism of a concussion is not as easy to identify, but may occur more frequently. Have you seen a difference in return to play in those that were pulled out right after an injury compared to athletes that continued to play with concussion signs and symptoms?

Written by: Jane McDevitt MS, ATC, CSCS
Reviewed by: Jeffrey Driban

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Beckwith JG, Greenwald RM, Chu JJ, Crisco JJ, Rowson S, Duma SM, Broglio SP, McAllister TW, Guskiewicz KM, Mihalik JP, Anderson S, Schnebel B, Brolinson PG, & Collins MW (2013). Timing of Concussion Diagnosis Is Related to Head Impact Exposure Prior to Injury. Medicine and Science in Sports and Exercise, 45 (4), 747-754 PMID: 23135364

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