To the best of our knowledge, this study is the first to demonstrate that ImPACT testing in the ED is correlated with testing at follow-up. We also found that neurocognitive testing in the ED provides an objective measure of neurocognitive deficits, and detects differences in concussion severity that cannot be identified with clinical concussion grading. The accurate assessment of injury severity and consequent outpatient management may decrease recovery time, reduce risk of secondary complications, and improve outcomes.13,23,37,38
The importance of early concussion management is underscored by the considerable morbidity following concussion that we found in this population. Expert consensus recommends that patients refrain from returning to full activity until their symptoms have resolved.16
Unfortunately, we found that at two weeks post-concussion, a number of patients had returned to normal activity before
symptom resolution, and therefore placed themselves at increased risk for further injury. Conversely, we found that patients who completed follow-up testing were more likely to report a gradual return to normal activity and wait to return to full activity until symptoms had resolved.
While ED ImPACT was valid in three out of four composite test domains, memory domains seemed to have the least correlation with follow-up scores. Memory domains may be more affected by the immediate symptoms of concussion, such as amnesia. While the ED verbal memory domain displayed moderate correlation with follow-up scores, the visual memory domain displayed no correlation at all. In general, ED scores for the visual memory domain were lower than scores for the three other test domains. This was only noted in our study and may be unique to testing in this setting or within hours of concussive injury.
Majerske and colleagues recently published a retrospective study of patients treated at a concussion center that demonstrated a complex association between post-concussive activity level and outcome using ImPACT scores.39
Using a five-point activity scale coded on chart review, the study found that patients with both the lowest and
highest levels of activity post-injury did poorly on follow-up neurocognitive testing using ImPACT.39
Our study did not find any association between reported post-concussion activities (e.g. sleep, physical activity, school attendance) and recovery times. However, we did find a correlation between completing follow-up and reporting a delay in return to full activity that was not associated with differences in symptom severity. One explanation for this finding may be improved compliance with discharge recommendations in patients who completed follow-up. This improved compliance may represent a beneficial effect follow-up had on reinforcing a safe and slow return to activity. An alternative explanation is that patients who follow up may inherently be more compliant. It is possible that those patients who did follow up were more invested in their treatment and recovery, and therefore more adherent to advice given regarding returning to normal activity.
We did not find a correlation between ImPACT scores and symptom duration or return to normal activity. While these are subjective measures, they are currently the outcomes of primary importance. Defining recovery following concussion remains a challenge for clinicians and researchers. Past studies of concussion recovery have found that in concussed patients, cognitive recovery often lags behind symptom recovery.40
Additionally, adolescents are known to under-report symptoms.41
ImPACT has been able to detect neurocognitive deficits that persist after resolution of self-reported symptoms.22,23
These findings have prompted sports concussion specialists to recommend that adolescent athletes achieve both symptom resolution and
normalization of neuropsychological measures before returning to play.14
Given the increased importance of neuropsychological measures, assessment early in the course of injury may help guide management. We did establish that the ED ImPACT can be used as an objective measure of acute concussion severity. Patients and clinicians may not be invested in cases of concussion where the patient does not display overt symptoms. Nonetheless, neurocognitive testing has demonstrated that in many asymptomatic patients, persistent dysfunction following concussion still exists.23,42
In the outpatient setting, this ability to detect subtle dysfunction has been used to motivate patients to comply with rest recommendations. Neurocognitive testing in the ED may prove to be equally motivating. The addition of neurocognitive testing to the tools available in the ED shifts the paradigm from passive evaluation of acute concussion to comprehensive evaluation and active management. Future studies should be directed at the ability of ED neurocognitive testing to increase compliance with discharge recommendations and improve outcomes.
The ability of ED ImPACT to gauge severity may also allow it to serve as a research tool in future efforts to evaluate the effect of individualized concussion management recommendations or novel treatment strategies (e.g., mandatory athletic or academic rest, symptom-based pharmacology) on outcomes.