This study sought to replicate previous research14,15
by evaluating baseline performance in those with and without a history of self reported concussion on two computerised neurocognitive assessments. Our data indicate that baseline performance on the CRI and ImPACT concussion assessments do not differ between subjects reporting up to three previous concussions. This information is part of a growing body of literature suggesting that either concussions do not result in chronic changes to cognitive functioning or the computerised neurocognitive batteries administered here do not provide adequate sensitivity to detect subtle decrements.
The evaluation by Iverson et al14
of a mixed sample of high school and amateur athletes showed no differences in performance in those with and without a history of concussion. Athletes were divided by self reported concussion history (up to two) and evaluated on the computerised ImPACT concussion assessment test. The authors concluded that if any long term deficits resulted from concussion, they were small and probably negligible. The evaluation by Collie et al15
of Australian footballers reporting up to four or more previous concussions also found no difference in baseline performance. Other assessments using pencil and paper assessments of exclusively collegiate13
and professional athletes20
have shown no difference in neurocognitive performance in those with and without a history of concussion. Guskiewicz et al13
reported similar performance in baseline assessments of 187 participants on a pencil and paper neuropsychological test battery between those reporting previous concussion (up to two) and those without previous injury. In addition, professional American footballers with a history of three or more concussions also showed no difference on a similar pencil and paper assessment battery when compared with those with fewer than three injuries.20
Non‐significant differences between groups with and without a self reported concussion history may have resulted from one of two possibilities. Firstly, no true differences in neurocognitive functioning may exist between those with and without a history of concussion. Sport related concussion has been described as a transient change in neural functioning, rather than a structural change, which resolves spontaneously within a short time.1
Animal model studies have shown that a large flux in ions within the cerebral tissue occurs at the time of injury. The imbalance ultimately corrects itself in 7–10 days21
with the potential for cognitive impairment to occur in the interim. Once the ion shift is corrected, cognitive functioning is restored to the pre‐injury state with no long term deficits.
Secondly, Iverson et al14
stated that, if chronic neurocognitive changes do result from concussion, they may be exceptionally small. This would suggest that the computer based concussion assessments used by Iverson et al
and in this study may not be sensitive to subtle changes in neurocognitive performance associated with the potentially chronic effects of concussion. Previous authors have suggested that one advantage of computer based assessments over the pencil and paper batteries is improved sensitivity to slight changes in cognitive performance immediately after injury. In particular, computer assessments can accurately measure reaction time to the thousandth of a second.22
Our data did not show differences between groups with and without a self reported concussion history, although it is not known if this aspect of cognitive functioning was directly affected by the injury. If the injury vitiated this cognitive feature, then normal functioning was restored to a level that is undetectable by the computerised tests.
Less sophisticated assessment methodologies have proven effective in detecting long term changes in cerebral functioning after concussion. Collins et al11
performed baseline evaluations on 393 collegiate American football athletes using a pencil and paper assessment battery. The 78 athletes who reported two or more previous concussions performed worse on the trail making B and symbol digit modalities tests than those with no concussion history or only one previous concussive injury. Athletes with only one previous concussive injury did not differ from those reporting no concussion history. This sample included athletes reporting a diagnosed learning disability, but no interaction between reported concussion history and a learning disability on neurocognitive performance was reported. A similar battery of tests was also used to evaluate the baseline performance of 618 jockeys who reported previous concussive injuries. Significantly worse performance was reported on the digit‐symbol and colour trails 2 tests.12
Significant differences seen on pencil and paper tests in these studies may have resulted from measuring different cognitive domains from those assessed by the computerised tests.
The use of a neurocognitive evaluation should continue to be included in the concussion assessment protocol. The CRI and ImPACT tests are both sensitive to acute changes in neurocognitive functioning immediately after concussion. Schatz et al17
evaluated 72 concussed athletes and 66 non‐concussed athletes using the ImPACT test. The test correctly identified 82% of the concussed participants. Similarly, Erlanger et al16
reported that 88% of 26 concussed participants were borderline or impaired on cognitive function on one or more of the CRI indices. Sensitivity to concussion may be improved when self reported symptomatology is also evaluated immediately after injury.23
What is already known on this topic
- Transient changes in cognitive status are often reported to result from sport related concussion
- Research is mixed on the long term effects of concussion on neurocognitive functioning
What this study adds
- This study adds to a growing body of literature indicating that athletes who report a previous history of concussion do not differ from those without a concussion history on computerised baseline neurocognitive assessments
Although this study supports other literature showing no difference in baseline performance in those reporting a history of concussions, certain confounding variables may be present in our retrospective study design. The cross sectional analysis does not permit the tracking of individual subject performance and evaluation of cognitive changes that may have occurred with each successive concussion. A prospective investigation tracking the collective influence of concussions on cognitive functioning may better elucidate this matter. The study design also did not allow us to verify self reported data, leaving the potential for differences in the true number of previous concussions sustained by our participants and the quantity reported. Using a large sample of high school athletes, McCrea et al24
found that nearly 53% of concussed athletes did not report their injury to any medical staff. The under‐reporting of concussions was related to a lack of comprehension of the importance of the injury, and 36% of the injured athletes did not recognise that they had sustained a concussion. We therefore find it feasible that concussions may have occurred during sport participation before baseline testing at the current institution. The validity of self reported concussion history may be decreased if concussive injuries went unreported.
Finally, we do not know the nature of any of the injuries. Most of the reported injuries were probably a result of sport participation and therefore probably mild traumatic brain injuries. Some injuries, however, may have resulted from other incidences such as falls or automobile accidents and may therefore have been more severe. Other information on the presence or absence of amnesia, loss of consciousness, length of confusion after injury, and duration of symptoms may also have provided some insight into the concussion severity.