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

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where the player was not immediately withdrawn and continued to play, and a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?

by: Jane McDevitt MS, ATC, CSCS


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