The battery we use as the basis for our model includes both computerized and paper-and-pencil measures. Although the use of paper-and-pencil measures can be logistically more complex and expensive than using computerized tests alone because they require fact-to-face administration, including such tests is likely to increase the sensitivity of the battery. Also, if neuropsychological tests are only used post-concussion, then the cost of administration is considerably lower.

Computerized tests. Computerized tests include the ImPACT [24] and the Vigil Continuous Performance Test (CPT) [25]. The following summary indices from the ImPACT are included: verbal memory composite, visual memory composite, visuomotor speed composite, and reaction time composite. Average delay (a reaction time index) is used for the Vigil CPT. Although more recent versions of the ImPACT are available, we based our algorithm on the 2.0 version because of the availability of data for our evidence-based model. This version appears to be highly correlated with more recent (including online) versions of the ImPACT.

Paper–and–pencil tests. These measures include the HVLT-R [26] (total correct immediate and delayed recall), the Brief Visuospatial Memory Test-Revised (BVMT-R) [27] (total correct immediate and delayed recall), the SDMT [28] (total correct within 90 s), a modified Digit Span Test [29] (total correct forward and backward sequences), the PSU Cancellation Task [30] (total correct within 90 s), Comprehensive Trail Making Test Trails 2 and 4 or 3 and 5 (CTMT) [31] (completion times for both parts), and the Stroop Color-Word Test (SCWT) [32] (time to completion for both color-naming and color-word conditions). Thus, across computerized and paper-and-pencil measures there are 17 test indices.

For most of the tests used, we suggest that alternate forms be used. The ImPACT has such alternate forms built into the program; alternate forms are available for all of the above paper-and-pencil tests with the exception of the modified Digit Span Test and SCWT.

Self–report. To measure post-concussion symptoms, we use the Post-Concussion Symptom Scale (PCSS). This measure includes a list of 22 common post-concussion symptoms. Examinees rate the extent to which they are currently experiencing each symptom on a scale from 0 to 6, with 0 indicating the absence of the symptom, and 6 being severe.

As Fig. 3.1 shows, each step of the algorithm after the initial neuropsychological testing involves a question, and then an action depending on the answer to the question.

Step 1. The action at Step 1 is to administer the test battery at 24–72 h post-injury. The evidence basis for this stems from animal models showing that many elements of the neurochemical cascade in the brain following concussion peak at about 48 h post-injury, and the decrease in glucose metabolism that occurs at about 48 h post-injury is correlated with cognitive dysfunction in adult rats [33–35]. Also, neurocognitive research in humans has shown that the greatest cognitive impact post-concussion typically occurs within 24–72 h post-injury [1, 36–38], though there is considerable individual variability [38]. As such, testing athletes during this time interval should provide a likely estimate of the full impact of the concussion on the brain as manifested by neurocognitive test results. Also, if the athlete is free of neurocognitive impairment at this early stage (relative to base rates), then no further neurocognitive testing would necessarily need to be conducted post-concussion, and the RTP decision could be made based on other factors (e.g., self-reported symptoms, vestibular signs). If the athlete does show signs of neurocognitive impairment at this point, then the objective neurocognitive data could be used to assist in getting temporary academic accommodations while symptomatic (e.g., deferral of exams and other assignments, testing in a room free from distraction, extra time on exams). A more detailed rationale for testing at this early time point post-concussion, and possibly before self-reported symptom resolution, is provided below in the section entitled, “Why Recommend Testing During the Acute Concussion Phase?”

Step 2. The algorithm has different Step 2s for males and females because the study on which these specific decision rules are based revealed slightly different base rates for males and females. In this study, we examined baseline performance in 495 collegiate athletes on the same test battery outlined in this chapter [23], and impairment on a test was defined as performing 2 SDs or more below the mean of other athletes; borderline impairment was defined as 1.5 SD or greater below the mean. These criteria were used since currently there is no agreed upon definition of abnormally poor test performance on neuropsychological tests following concussion, and also to allow for some flexibility in decision making.

In this study, less than 10 % of males had five or more borderline scores, and less than 10 % of females had three or more borderline scores. Additionally, less than 10 % of males had three or more impaired scores, and less than 10 % of females had two or more impaired scores. We used these base rates as a foundation for the decision rules in our model. In light of such data, male athletes who are tested post-concussion who show impairment on three or more tests and female athletes who show impairment on two or more tests evidence highly unusual performance that is likely to reflect the impact of their concussion (see Fig. 3.1). Similarly, male athletes who are tested post-concussion who show borderline scores on five or more tests and female athletes who show borderline scores on three or more tests display highly unusual performance that is likely to reflect the impact of their concussion. The application of these data in decision rules is shown at Step 2 in Fig. 3.1.

Ideally, concussion programs adopting this algorithm would be advised to use a base rate of impairment data collected from athletes participating in their specific programs. In this way, the data used are likely to be most valid for that group of athletes for a particular neurocognitive test battery. If such base rates differ from what we report, relevant values could simply replace what we report from our athletes in the algorithm. If base rates of impairment are not available, it should be noted that other studies using test batteries of comparable length have reported similar base rates of impairment using a similar number of test indices in healthy older adults [39, 40], as well as children and adolescents [41]. Thus, although the direct evidence basis for this recommendation concerning base rates relies only on our one study of collegiate athletes, findings from these other studies suggest that these data are likely representative of base rates of impairment more generally when individuals are tested on a neurocognitive battery similar in length to ours. Also, the data we rely on for concrete decision rules in the algorithm can be thought of as a vehicle for describing the model rather than something to be rigidly applied. Again, ideally, local base rate norms based upon whatever battery of tests is used, if different from what we report, would replace the specific values in the algorithm.

If male or female athletes receive a “yes” response at Step 2, for either the impaired or borderline criterion, then the action is to “Administer Alternate Test Forms Once PCSS is Within Normal Limits.” The evidence basis for this stems from findings showing that even when athletes report that they are symptom free, many still show evidence for objective cognitive impairment [19]. Additionally, relying on self-report of cognitive functioning when determining when athletes can return to play is likely to be inaccurate given the consistently replicated low correlation found between objective neurocognitive test performance and self-reported neurocognitive functioning [22]. Thus, any athlete should have to perform within normal limits neurocognitively prior to returning to play, and such decisions should not be based on self-reported cognitive functioning alone. Following this recommendation after a “yes” response, the algorithm indicates, “Repeat Step 2, Then Conduct Follow-Up Testing as Clinically Indicated.”

Step 3. If either male or female athletes have a “no” response at Step 2, then the algorithm moves to Step 3 to consider the following question: “Is PCSS Within Normal Limits?” The determination of “within normal limits” is made using normative data from our sample of collegiate athletes at baseline on the PCSS. Similar to our comment above concerning the ideal framework being the use of local norms to determine base rates, normative data from local samples would ideally be applied here to the PCSS. Scores falling within the broad average range (i.e., standard score of 80 or above) are considered “within normal limits.” If the answer to this question is “yes,” then the recommendation is to begin the RTP protocol. If the answer is “no,” then the recommendation is to wait on starting the RTP until the PCSS is within normal limits.

One complicating issue involves cases where athletes have a “yes” response at Step 2 (meeting the below base rate impaired or a borderline criterion), yet report being within normal limits in terms of their symptom report. Given that the recommendation following such an outcome is to “Administer Alternate Test Forms Once PCSS is Within Normal Limits,” how does one proceed? There are no clear evidence-based guidelines for how to proceed here in terms of the precise timing of the next post-concussion testing point. A broad guideline would be to recommend testing the athlete again between 5–10 days post-concussion, given that many studies show that most collegiate athletes show full cognitive recovery by that point [1, 30, 36, 37, 42–44]. With that said, other research shows that some collegiate athletes do not recover within that window and take longer than two weeks for their neurocognitive functioning to normalize [44, 45]. Thus, more research will clearly be needed to refine this broad guideline. Studies that examine the duration for normalization of brain functioning in athletes who report being normal in terms of symptom report but show impairments neurocognitively would be ideal. Given the current state of the literature, the most prudent approach would be to rely more on individualistic clinical concussion management strategies employed by skilled clinicians to determine temporal sequencing of testing in these cases [46]. Factors, such as the urgency with which an RTP decision needs to be made (e.g., if a crucial game is imminent vs. the athlete’s sport not being “in season”), as well as other individualistic factors (e.g., prior concussion history, the presence of clinically significant depression), would need to be considered. Thus, the model allows for considerable flexibility at this stage not only due, in part, to the absence of clear research evidence to guide decision making, but also due to idiosyncratic factors that are nearly always going to be at play in the clinical management of concussion.

One potentially controversial recommendation in our algorithm is to routinely test athletes in the acute stage more systematically post-concussion. Many athletes are likely to still be experiencing some symptoms at the 24–72 h post-concussion point, and some investigators and clinicians have asserted that such testing should be avoided on a number of grounds. First, given that athletes are still symptomatic, some posit that such testing cannot contribute anything to the RTP decision, because clinicians are typically not going to put athletes back to play who are still experiencing self-reported symptoms. Second, it has been suggested that such testing could exacerbate the athlete’s symptoms. These are reasonable concerns; however, to our knowledge, there is no published study showing that recently concussed, still symptomatic adult athletes show more of an increase in symptoms following such neurocognitive testing than healthy controls. We assert that the value of such acute testing outweighs the potential minor risk (as yet empirically undemonstrated) of a temporary increase in symptoms. The caveat to this, of course, involves cases where symptoms are so severe that testing could be harmful in exacerbating already severe symptoms, or where the nature of such symptoms would likely substantially interfere with test performance (e.g., severe dizziness, nausea, or headache, among others). This is where individualistic concussion management again becomes important [46].