Self-report post-concussion symptom scales have been a key methodology in monitoring recovery from sport-related concussion, and assisting in return-to-play decision-making. To date, however, the scales employed for this purpose have been constructed on the basis of clinical judgment and no single scale has been identified as a “gold standard” for this purpose. The newly derived Concussion Symptom Inventory (CSI) is presented in the Appendix. To our knowledge, this is the first scale that has been empirically derived for the purpose of monitoring subjective symptoms following concussion. The source data also constitute the largest sample of prospectively studied cases of concussion in the literature to date, with a concussed sample size of 641 athletes compared with a baseline sample of 16,350 athletes. We have elected to include space on the form for the scale for the recording of any additional subjectively reported symptom that a clinician believes may have been due to the concussion. This will allow for a full clinical documentation of subjective symptomatology, including symptoms that were very rarely reported (or not queried) in our prospective studies. We are not proposing specific “cut-off” scores, because we lack sufficient empirical data at this point to suggest that there actually is a quantifiable risk of returning a player to competition based upon a particular CSI score. This is, of course, true of any symptom scale or other technique for measuring impairment following concussion.
We propose that athletic trainers and team medical personnel employ the CSI as a standardized methodology for tracking symptom resolution following concussion, and incorporate the information from the CSI into clinical decision-making regarding return-to-play. This recommendation is appropriate, given the lack of empirically derived alternative scales to date. The decision-making process regarding return-to-play should be informed by the evolving literature on the natural history and outcome of sport-related concussion, and by the specific clinical circumstances of the individual player. It is important to emphasize that the CSI is not intended to constitute the sole basis for clinical decision-making in the medical management of sport-related concussion, and that individual players may also experience concussion-related symptoms (e.g., sleep disturbance) that are not recorded within the CSI owing to the relative infrequency with which they occurred in our concussed sample. We do not intend for athletic trainers or team medical personnel to rely solely upon the results of the CSI to determine recovery.
The CSI does, however, provide an empirically based, rapid, and systematic methodology for tracking subjective symptoms following sport-related concussion. To date, a variety of symptom scales have been used in clinical assessments and studies of the natural history of concussion, and item selection and scaling have been driven by clinical judgment rather than empirical data. This large sample of players with baseline and post-concussion data allowed us to eliminate a number of items that proved to be largely insensitive to concussion.
The risks of “premature” return-to-play following sport-related concussions are as yet poorly delineated, and none of the many guidelines that have been promulgated for this purpose are evidence-based. They are all in agreement, however, that players should be symptom-free before being cleared to return. This would seem to be a reasonable and appropriately conservative approach to concussion management, particularly in younger athletes, until additional data regarding risks are accrued and clinical decision-making can be driven by reliable evidence. The CSI constitutes a relatively rapid, standardized way of monitoring symptom recovery, with no loss in sensitivity or reliability in comparison with much longer inventories. It has been demonstrated that concussed athletes routinely endorse subjective symptoms for at least as long as impairment is typically detectable by more time-consuming and expensive methodologies (e.g., neuropsychological testing), despite concerns that players might under-report symptoms in order to be cleared to return-to-play. Finally, recent publications, including a consensus paper, have recommended that players should be asymptomatic before screening for impairment using any type of neuropsychological testing, further underscoring the central role of subjective symptom checklists in monitoring recovery from concussion.
Although the CSI was derived from sport-related concussion data and the primary utility of the scale is intended to be for this purpose, it is conceivable that the scale might also prove useful in studies of the natural history of concussion due to other causes. To date, there is no clear consensus regarding a specific scale for use in tracking recovery of symptoms from concussion/mild traumatic brain injury in clinical (non-athletic) populations. Although the CSI has not yet been validated for applications outside of sports, it may have some appeal owing to the fact that it was empirically derived from data obtained from injured athletes. This population is typically highly motivated to recover, and therefore would be unlikely to over-endorse symptoms as a result of psychological factors (e.g., depression, somatoform tendencies, malingering). Although the CSI is clearly composed of a number of symptoms that are not exclusively specific to concussion (e.g., headache, drowsiness), it is reasonably safe to assume that the symptoms that were retained for this scale were in fact generated by concussion and not by other factors that might be operating in some proportion of mild TBI patients recruited from a non-sports setting.