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Instrumenting the Balance Error Scoring System for Use With Patients Reporting Persistent Balance Problems After Mild Traumatic Brain Injury

Published:November 07, 2013DOI:https://doi.org/10.1016/j.apmr.2013.10.015

      Abstract

      Objective

      To determine whether alterations to the Balance Error Scoring System (BESS), such as modified conditions and/or instrumentation, would improve the ability to correctly classify traumatic brain injury (TBI) status in patients with mild TBI with persistent self-reported balance complaints.

      Design

      Cross-sectional study.

      Setting

      Outpatient clinic.

      Participants

      Subjects (n=13; age, 16.3±2y) with a recent history of concussion (mild TBI group) and demographically matched control subjects (n=13; age, 16.7±2y; control group).

      Interventions

      Not applicable.

      Main Outcome Measures

      Outcome measures included the BESS, modified BESS, instrumented BESS, and instrumented modified BESS. All subjects were tested on the noninstrumented BESS and modified BESS and were scored by visual observation of instability in 6 and 3 stance conditions, respectively. Instrumentation of these 2 tests used 1 inertial sensor with an accelerometer and gyroscope to quantify bidirectional body sway.

      Results

      Scores from the BESS and the modified BESS tests were similar between groups. However, results from the instrumented measures using the inertial sensor were significantly different between groups. The instrumented modified BESS had superior diagnostic classification and the largest area under the curve when compared with the other balance measures.

      Conclusions

      A concussion may disrupt the sensory processing required for optimal postural control, which was measured by sway during quiet stance. These results suggest that the use of portable inertial sensors may be useful in the move toward more objective and sensitive measures of balance control postconcussion, but more work is needed to increase sensitivity.

      Keywords

      List of abbreviations:

      AP (anterior-posterior), AUC (area under the curve), BESS (Balance Error Scoring System), ML (mediolateral), mTBI (mild traumatic brain injury), NIH (National Institutes of Health), OHSU (Oregon Health & Science University), RMS (root-mean-square), ROC (receiver operating characteristic), TBI (traumatic brain injury)
      Because mild traumatic brain injury (mTBI) or concussion frequently goes unreported, the estimated annual U.S. incidence of 1.6 to 3.8 million likely reflects an underestimation.
      • Langlois J.A.
      • Marr A.
      • Johnson R.L.
      Tracking the silent epidemic and educating the public: CDC's traumatic brain injury-associated activities under the TBI Act of 1996 and the Children's Health Act of 2000.
      • McCrea M.
      • Hammeke T.
      • Olsen G.
      • Leo P.
      • Guskiewicz K.
      Unreported concussion in high school football players: implications for prevention.
      Additionally, a recent mTBI increases the risk of sustaining a second mTBI,
      • Barkhoudarian G.
      • Hovda D.A.
      • Giza C.C.
      The molecular pathophysiology of concussive brain injury.
      • Guskiewicz K.M.
      • McCrea M.
      • Marshall S.W.
      • Randolph C.
      • Barr W.
      • Kelly J.P.
      Cumulative effects associated with recurrent concussion in collegiate football players: the NCAA Concussion Study.
      • Laurer H.L.
      • Bareyre F.M.
      • Lee V.M.
      • et al.
      Mild head injury increasing the brain's vulnerability to a second concussive impact.
      and the sequelae of repetitive mTBI may be cumulative.
      • McCrory P.
      Sports concussion and the risk of chronic neurological impairment.
      Therefore, premature return to play confers serious risk for further brain injury.
      • Wetjen N.M.
      • Pichelmann M.A.
      • Atkinson J.L.
      Second impact syndrome: concussion and second injury brain complications.
      A disturbance in balance is a commonly reported symptom post-traumatic brain injury (TBI). The most frequently used clinical scale for postconcussion balance assessment is the Balance Error Scoring System (BESS). The BESS measures instability by the examiner's subjective count of errors in the maintenance of various stances by the patient, who has his/her eyes closed (feet together, single-leg, and tandem stance) and is standing on different surfaces (firm and foam).
      • Riemann B.L.
      • Guskiewicz K.M.
      Effects of mild head injury on postural stability as measured through clinical balance testing.
      Although portable and quick to administer, the BESS suffers from learning,
      • Broglio S.P.
      • Zhu W.
      • Sopiarz K.
      • Park Y.
      Generalizability theory analysis of balance error scoring system reliability in healthy young adults.
      • Mulligan I.J.
      • Boland M.A.
      • McIlhenny C.V.
      The Balance Error Scoring System learned response among young adults.
      practice,
      • Valovich T.C.
      • Perrin D.H.
      • Gansneder B.M.
      Repeat administration elicits a practice effect with the Balance Error Scoring System but not with the standardized.
      and fatigue
      • Wilkins J.C.
      • McLeod T.C.
      • Perrin D.H.
      • Gansneder B.M.
      Performance on the Balance Error Scoring System decreases after fatigue.
      effects and may be insensitive to mild impairments.
      • Valovich McLeod T.C.
      • Bay R.C.
      • Lam K.C.
      • Chhabra A.
      Representative baseline values on the Sport Concussion Assessment Tool 2 (SCAT2) in adolescent athletes vary by gender, grade, and concussion history.
      These factors represent questions about the validity and reliability of the BESS and the decisions emanating from its use.
      A recent shortened version of the BESS, the modified BESS test, includes only 3 stances on firm surface (omitting the 3 stances on the foam surface). The modified BESS was published as a part of the Sport Concussion Assessment Tool 2
      • McCrory P.
      • Meeuwisse W.
      • Johnston K.
      • et al.
      Consensus statement on concussion in sport–the 3rd International Conference on concussion in sport, held in Zurich, November 2008.
      • McCrory P.
      • Meeuwisse W.H.
      • Aubry M.
      • et al.
      Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012.
      and has published norms
      • Valovich McLeod T.C.
      • Bay R.C.
      • Lam K.C.
      • Chhabra A.
      Representative baseline values on the Sport Concussion Assessment Tool 2 (SCAT2) in adolescent athletes vary by gender, grade, and concussion history.
      • Iverson G.L.
      • Koehle M.S.
      Normative data for the modified balance error scoring system in adults.
      but may also have problems with sensitivity. A recent study reported no differences in the modified BESS between high school students with and without concussion.
      • Valovich McLeod T.C.
      • Bay R.C.
      • Lam K.C.
      • Chhabra A.
      Representative baseline values on the Sport Concussion Assessment Tool 2 (SCAT2) in adolescent athletes vary by gender, grade, and concussion history.
      The authors suggested that the modified BESS may have a ceiling effect, and the presence of foam in the full BESS may be more helpful at classifying those with and without mTBI. However, the full BESS has known psychometric weaknesses and, similar to the modified BESS, also uses subjective scoring. Objective measures of persisting balance complaints could greatly augment patient safety determinations.
      Currently, self-report questionnaires and subjectively scored clinical tests, such as the BESS, represent the most frequently used method of evaluating and monitoring postinjury complaints. Reliance on these measures for return to play and medical management can have grave consequences. A trend toward underreporting mTBI sequelae has been reported in high school and college-aged athletes.
      • Broglio S.P.
      • Macciocchi S.N.
      • Ferrara M.S.
      Neurocognitive performance of concussed athletes when symptom free.
      • Field M.
      • Collins M.
      • Lovell M.R.
      • Maroon J.
      Does age play a role in recovery.
      • Van Kampen D.A.
      • Lovell M.R.
      • Pardini J.E.
      • Collins M.W.
      • Fu F.H.
      The “value added” of neurocognitive testing after sports-related concussion.
      Many young people experience social pressure to return to their sport before symptoms have fully resolved, which is contrary to their best interests. The widespread use of self-report measures coupled with the tendency to underreport symptoms have prompted the call for more objective forms of measurement.
      The instrumentation of clinical motor tests is increasingly used to achieve objective quantification of movement.
      • Palmerini L.
      • Mellone S.
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      • Valzania F.
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      Quantification of motor impairment in Parkinson's disease using an instrumented timed up and go test.
      • Weiss A.
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      • Plotnik M.
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      • Giladi N.
      • Hausdorff J.M.
      An instrumented timed up and go: the added value of an accelerometer for identifying fall risk in idiopathic fallers.
      Because balance represents a physically measureable attribute, it lends itself naturally to a technology-based measurement solution. Inertial sensors, the size of a wristwatch, contain accelerometers, gyroscopes, and magnetometers, which can objectively capture subtle anomalies when integrated properly. Various types of inertial sensors have begun to yield evidence of validity and reliability for balance measurement in people with mild or early Parkinson's disease,
      • Mancini M.
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      • Zampieri C.
      • Carlson-Kuhta P.
      • Nutt J.G.
      • Chiari L.
      Trunk accelerometry reveals postural instability in untreated Parkinson's disease.
      • Mancini M.
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      • Carlson-Kuhta P.
      • et al.
      ISway: a sensitive, valid and reliable measure of postural control.
      multiple sclerosis,
      • Spain R.I.
      • St. George R.J.
      • Salarian A.
      • et al.
      Body-worn motion sensors detect balance and gait deficits in people with multiple sclerosis who have normal walking speed.
      and also in older adults.
      • Mancini M.
      • King L.
      • Salarian A.
      • et al.
      Mobility lab to assess balance and gait with synchronized body-worn sensors.
      Software

      APDM movement monitoring solutions. 2013.

      associated with these sensor readings can automatically calculate a myriad of metrics based on the features of human movement, making it feasible for preprogrammed, nonexpert administration. For example, postural sway during quiet stance can be characterized by its amplitude, frequency, and velocity. The National Institutes of Health (NIH) Balance Toolbox recently began promoting the use of inertial sensors to assess general balance (nondisease specific) through postural sway. Specifically, the NIH recommends the Standing Balance Test that measures anterior-posterior (AP) postural sway during different stance conditions (feet together and tandem on firm and foam surfaces). However, what is generally referred to as balance is composed of many more elements than postural sway.

      Horak FB, Macpherson JM. Postural orientation and equilibrium. In: Rowell LB, Shepherd JT, editors. Handbook of Physiology. Exercise: Regulation and Integration of Multiple Systems. New York: Oxford; 1996. p 255-92.

      Additionally, postural sway can be measured in more basic dimensions than the AP direction (ie, ML). Currently, it is not known which sway features and balance conditions are most frequently impaired after mTBI. A recent study showed that the NIH-recommended Standing Balance Test protocol was inferior to the BESS in separating those with and without mTBI,
      • Furman G.R.
      • Lin C.C.
      • Bellanca J.L.
      • Marchetti G.F.
      • Collins M.W.
      • Whitney S.L.
      Comparison of the balance accelerometer measure and balance error scoring system in adolescent concussions in sports.
      which, as previously discussed, has demonstrated its own set of weaknesses.
      • Broglio S.P.
      • Zhu W.
      • Sopiarz K.
      • Park Y.
      Generalizability theory analysis of balance error scoring system reliability in healthy young adults.
      • Mulligan I.J.
      • Boland M.A.
      • McIlhenny C.V.
      The Balance Error Scoring System learned response among young adults.
      • Valovich T.C.
      • Perrin D.H.
      • Gansneder B.M.
      Repeat administration elicits a practice effect with the Balance Error Scoring System but not with the standardized.
      • Finnoff J.T.
      • Peterson V.J.
      • Hollman J.H.
      • Smith J.
      Intrarater and interrater reliability of the Balance Error Scoring System (BESS).
      • Giza C.C.
      • Kutcher J.S.
      • Ashwal S.
      • et al.
      Summary of evidence-based guideline update: evaluation and management of concussion in sports: report of the Guideline Development Subcommittee of the American Academy of Neurology.
      The authors suggest that the Standing Balance Test was not developed directly for concussion but rather as a general balance screening; however, the BESS was directly developed to assess balance after mTBI. To our knowledge, no studies have yet attempted to instrument the BESS directly using an inertial sensor to improve objective assessment of balance deficits.
      The purpose of this study was to determine whether alterations to the BESS, such as modified conditions and/or instrumentation, would improve the ability to correctly classify participants according to TBI status. We hypothesized that addition of the foam conditions would improve diagnostic accuracy of the BESS over the modified BESS and instrumentation of the BESS would improve diagnostic accuracy over the noninstrumented BESS.

      Methods

      Ethical review

      The Oregon Health & Science University (OHSU) Institutional Review Board approved this study. All participants enrolled in the study received and signed informed consent forms approved by the OHSU Institutional Review Board. A legal guardian accompanied participants <18 years old, and subjects ≤16 years signed an additional assent form. All work was conducted in accordance with the Declaration of Helsinki (1964).

      Recruitment

      The mTBI participants were recruited from the OHSU Sports Medicine Department and the Department of Rehabilitation Services. All mTBI participants, who were diagnosed by a physician in the Department of Sports Medicine, were 2 to 13 months status post-mTBI. All were currently receiving standardized outpatient rehabilitation services for their complaints of continued imbalance and dizziness. Exclusion criteria included recent orthopedic injuries, other neurologic or vestibular disorders unrelated to their brain injury, or outside the age range of 13 to 19 years old. Healthy age-matched control participants were recruited through advertisements in local community media. The control participants were excluded from participation if there was a history of mTBI, other neurologic or vestibular disorders, or any recent orthopedic injuries. A total of 30 subjects were screened for this study. Four were unable to participate because of scheduling conflicts.

      Participant characteristics

      Thirteen participants with mTBI (age, 16.3±1.6y; height, 164.3±7cm; weight, 62.4±12.6kg; sex: 3 boys, 10 girls) and 13 demographically matched healthy controls (age, 16.7±2.1y; height, 166.7±6cm; weight, 59.1±9.1kg; sex: 3 boys, 10 girls) completed the study protocol (N=26). The mTBI group's average time postinjury was 5±3.3 months with causes as follows: motor vehicle collision (n=3), soccer (n=4), lacrosse (n=1), wakeboarding (n=1), weightlifting (n=1), horseback riding (n=1), playing on a playground (n=1), and falling out of bed (n=1).

      Design and procedure

      This study used a cross-sectional case/control design. Each participant was tested at OHSU's Rehabilitation Services Department on the following 4 primary measures: BESS, modified BESS, instrumented BESS, and the instrumented modified BESS. The BESS and modified BESS were instrumented by adding an inertial sensor (Opal)a at L5 with an elastic belt (fig 1). The Opal included 2 linear accelerometers (mediolateral [ML] and AP) to detect postural sway displacement at 120Hz that was wirelessly transmitted to a laptop using Mobility Lab software.
      • Mancini M.
      • King L.
      • Salarian A.
      • et al.
      Mobility lab to assess balance and gait with synchronized body-worn sensors.
      ,a Postural sway was automatically quantified in both the AP and ML directions during each stance condition of these clinical tests by calculating the root-mean-square (RMS) around the mean acceleration (acc), a metric representing sway dispersion (RMS=APacc2+MLacc2). RMS has demonstrated excellent reliability in different populations.
      • Mancini M.
      • Salarian A.
      • Carlson-Kuhta P.
      • et al.
      ISway: a sensitive, valid and reliable measure of postural control.
      Most importantly, any physical error occurring during standing tasks (ie, losing balance) would be reflected in a larger RMS value of bidirectional sway.
      Table 1 details specific test conditions and outcome measurements for the BESS, modified BESS, instrumented BESS, and instrumented modified BESS. The BESS and modified BESS were administered per the published instructions
      • Riemann B.L.
      • Guskiewicz K.M.
      Effects of mild head injury on postural stability as measured through clinical balance testing.
      by an experienced and licensed physical therapist. Participants were scored subjectively by examiner judgment of errors, which were summed for the total. For example, if the participant opened their eyes or took their hand(s) off their hips, each was counted as 1 error (total score of 10 errors per condition or 60 points possible for errors). Both the instrumented BESS and instrumented modified BESS were administered simultaneously to the noninstrumented testing as the data were gathered by the sensors and transmitted wirelessly to a computer. For both instrumented tests, the RMS was automatically calculated by the Ambulatory Parkinson's Disease Monitoring Inc software and was later averaged over all conditions.
      Table 1Description of the 4 balance tests conducted in this study
      TestNoninstrumentedInstrumented
      BESS (6 trials)
       Body positions
      • Feet together stance
      • Single-leg stance
      • Tandem stance
      • Feet together stance
      • Single-leg stance
      • Tandem stance
      Eyes closed for all trialsEyes closed for all trials
       Standing conditions
      • Firm surface
      • Foam surface
      • Firm surface
      • Foam surface
      20 seconds for all trials30 seconds for all trials
       MeasureSubjective counting of errors in body position

      Scored (0–10, minimum=0, maximum=60)
      Sway

      RMS (m/s2)
      Modified BESS (3 trials)
       Body positions
      • Feet together stance
      • Single-leg stance
      • Tandem stance
      • Feet together stance
      • Single-leg stance
      • Tandem stance
      Eyes closed for all trialsEyes closed for all trials
       Standing conditions
      • Firm surface
      • Firm surface
      20 seconds for all trials30 seconds for all trials
       MeasureSubjective counting of errors in body position

      Scored (0–10, minimum=0, maximum=30)
      Sway

      RMS (m/s2)

      Statistical analysis

      Stata version 11b was used to complete preliminary analyses and hypothesis testing. Unpaired t tests were computed to verify the successful matching of demographic variables between groups. Independent sample t tests were also calculated for each version of the balance test to determine whether it could detect mean group differences between diagnostic categories. In order to assess our hypotheses about diagnostic accuracy, we computed receiver operating characteristic (ROC) curve area under the curve (AUC) values with the methods developed by Janes et al
      • Janes H.
      • Longton G.
      • Pepe M.
      Accommodating covariates in ROC analysis.
      in their contributed Stata routines (roccurve and comproc). These routines use bootstrap calculations (with 3000 trials used) for P values. Each P value represents the null hypothesis that any difference in the ROC AUC occurred because of random sampling alone. To focus on the relevant part of the ROC curves, the AUC is restricted to a false positive rate <.50.

      Results

      As expected, no significant differences appeared for demographic variables between the mTBI and control groups: age (t=.59, P=.56), height (t=.95, P=.35), or weight (t=−.78, P=.44). Table 2 presents the comparison of balance tests between the mTBI and control groups. Scores from the BESS and modified BESS were similar between groups. However, results from the instrumented versions of both of these tests were significantly different between groups. However, if adjusted for multiple comparisons for the 4 t tests, only the instrumented modified BESS remained significant. Figure 2 shows individual scores for each test.
      Table 2Mean ± SD and CI for the balance measures and comparisons between the mTBI group and age-, height-, and weight-matched controls
      TestsControlmTBIP (t)
      BESS (no. of errors)13.50±6.35(9.70–17.40)18.5±9.67(12.70–19.40).13 (−1.56)
      Modified BESS (no. of errors)2.15±1.77(1.08–3.22)4.53±4.46(1.84–7.24).09 (−1.79)
      Instrumented BESS (RMS; m/s2)0.37±0.11(0.30–0.43)0.49±0.17(0.38–0.59).04 (−2.16)
      Instrumented modified BESS (RMS; m/s2)0.22±0.06(0.18–0.26)0.35±0.14(0.27–0.44).01 (−3.03)
      NOTE. Values are mean ± SD (95% CI) or as otherwise indicated.
      Abbreviation: CI, confidence interval.
      Figure thumbnail gr2
      Fig 2Frequency distributions for the 4 indicated balance tests: BESS (a), modified BESS (b), instrumented BESS (c), and instrumented modified BESS (d). The rows of square symbols indicate mean values. The P values are for 2-sample t tests. Abbreviations: Instr., instrumented; Mod., modified.
      In our sample of mTBI patients with persistent complaints of balance impairment or unsteadiness, we defined abnormal balance as 1.5 SD from the control group mean. Using this definition, we found sensitivity and specificity, respectively, to be the following: BESS (23%, 92%), modified BESS (31%, 85%), instrumented BESS (38%, 100%), and instrumented modified BESS (54%, 100%).
      Figure 3 presents the ROC AUC for all of the balance scales. To determine if the addition of foam increased the diagnostic accuracy, we compared the BESS to the modified BESS and found no difference in the AUC (P=.59). To determine if instrumentation of the BESS and modified BESS improved diagnostic accuracy, we compared the instrumented version of the BESS to the noninstrumented version and found that the ROC AUC of the instrumented modified BESS differed from that of the BESS (P=.032) and the modified BESS (P=.035). For completeness, we compared the instrumented BESS with the instrumented modified BESS and found that they did not differ significantly from one another (P=.09). Table 3 summarizes details of the ROC AUC for the balance measures.
      Figure thumbnail gr3
      Fig 3ROC curves for the TPR and FPR for each balance test. Abbreviations: FPR, false positive rate; Inst., instrumented; Mod., modified; TPR, true positive rate.
      Table 3Summarizes details of the ROC AUC per test
      TestAUCSE95% CI
      BESS.63.11.41–.85
      Modified BESS.64.11.42–.860
      Instrumented BESS.70.11.50–.910
      Modified instrumented BESS.81.09.64–.990
      Abbreviation: CI, confidence interval.

      Discussion

      The primary aim of this study was to determine whether alterations to the BESS (eg, modified conditions and/or instrumentation) would improve the ability to correctly classify participants according to TBI status. We found that (1) the addition of foam in the full version of the BESS, for both the noninstrumented and instrumented versions, did not improve its ability to differentiate between mTBI and control patients; and (2) using the instrumented modified BESS resulted in the highest diagnostic accuracy.
      The findings from the ROC AUC analysis performed in this study provide some practical considerations. The ROC AUC results suggest that using the instrumented modified BESS is better for distinguishing between groups and the foam stances did not add obvious value in postinjury classification. Our results suggested that adding instrumentation reduced classification errors. For example, in our sample of 13 athletes with persistent self-reported instability, only 3 (23%) would have been classified as having an abnormal score on the commonly used BESS, leading to premature return to play and missed treatment of a deficit receptive to rehabilitation.
      • Alsalaheen B.A.
      • Mucha A.
      • Morris L.O.
      • et al.
      Vestibular rehabilitation for dizziness and balance disorders after concussion.
      Conversely, by using one inertial sensor on the waist during the test, 31% more (7 of 13) athletes would be documented as abnormal. This difference has very real implications for clinical treatment and return-to-play determinations. However, sensitivity may be still too low to use as a single test for balance control.
      Our results did not agree with a recent article reporting the BESS' superiority to the accelerometer-based Standing Balance Test.
      • Furman G.R.
      • Lin C.C.
      • Bellanca J.L.
      • Marchetti G.F.
      • Collins M.W.
      • Whitney S.L.
      Comparison of the balance accelerometer measure and balance error scoring system in adolescent concussions in sports.
      One reason for differing results is that our study measured instrumentation of the BESS (designed for mTBI assessment) rather than the Standing Balance Test. Furthermore, our sway metric included both the AP and ML directions whereas the above mentioned study assessed path length only in the AP direction. Instability in the ML direction may be more sensitive to imbalance.
      • Mak M.K.
      • Ng P.L.
      Mediolateral sway in single-leg stance is the best discriminator of balance performance for Tai-Chi practitioners.
      Moreover, instability in the AP direction only, particularly in tandem stance conditions where less AP sway occurs naturally, may not reflect imbalance after mTBI.
      Postural sway represents a domain of balance, specifically static balance. Testing various stance positions while altering surface and visual inputs challenge one's ability to use sensory information for stability. Although postural sway represents the complex sensorimotor control of the nervous system required to maintain equilibrium during stance posture, it may not capture other important domains of balance, including dynamic or cognitive aspects of balance. Insult occurring at any level of efferent neural communication, including corticospinal tract, cerebral peduncles, corona radiate, internal capsule, or cerebellar peduncle, could result in suboptimal performance. Furthermore, vestibular nuclei connect to critical areas for balance (eg, cerebellum, cranial nerves [3, 4, and 6], thalamus, cortex, and spinal cord).
      • Herdman S.J.
      Vestibular rehabilitation.
      Each of these areas contributes to coordinated balance performance. Therefore, each patient may have an individualized balance profile, and measuring just one domain of balance may be insufficient.
      Accurate identification and treatment of balance disorders after mTBI are critical for adolescent athletes. Even subtle balance problems may disrupt academic, psychological, social, and physical development and may play a role in further concussions. If measurable deficits cannot be documented, the patient may not receive appropriate rehabilitation services. The mTBI management of adolescents is further complicated by a complex mix of psychosocial factors. Because of the patient's age and concurrent developmental processes, difficulties with social and emotional development can arise after injury. Sole reliance on subjective complaints can be misleading and underinformative.

      Study limitations

      A significant limitation to our study is the small sample size. With a larger sample size, the noninstrumented BESS may have detected group differences. A limitation of most balance studies is that a criterion standard for abnormality does not currently exist. The most frequently used measure is self-report. As such, we relied on self-report for this group of patients during rehabilitation after mTBI. As previously discussed, there is a documented tendency to underreport in this age group. Therefore, we purposely selected young people whose reported symptoms were not resolving and were delaying their return to play. As such, these complaints are likely to be valid. Additionally, our sample was fairly heterogeneous regarding time since injury, possibly resulting in the measurement of constituents from fundamentally different groups. Such limitations could limit the generalizability of our findings. Finally, our rater (L.A.K.) was not blinded to subject diagnosis, which represented a risk of investigator bias. However, knowledge of diagnostic classification would be expected to result in worse ratings for patients and better ratings for controls. Therefore, investigator bias would have been most likely to result in nonsignificant differences between noninstrumented and instrumented measures. In general, we found the opposite result, which mitigates our concern over this limitation.

      Conclusions

      This study highlights the potential of using inertial sensors to measure specific domains of balance control in adolescents who have sustained an mTBI. Because of the vast number of children affected by mTBI and because of the vulnerable stage of development, it is imperative to identify sensitive and specific measures. Annually, it is expected that at least 173,285 persons <20 years old will be treated for sports- and recreation-related TBI in emergency departments across the United States.
      • Centers for Disease Control and Prevention
      Nonfatal traumatic brain injuries related to sports and recreation activities among persons aged ≤19 years–United States, 2001-2009.
      With increasing evidence of long-term effects of repeated concussion, it is essential that complete recovery has occurred before returning to full activity. Until now, a sophisticated laboratory was required to perform postural tests of sway and gait analysis. These results suggest that the use of portable inertial sensors may be useful in the move toward more objective measures of balance control postconcussion, but more work is needed to improve levels of sensitivity.

      Suppliers

      • a.
        APDM Inc, 2828 Southwest Corbett Ave, Ste 130, Portland, OR 97201.
      • b.
        StataCorp, 4905 Lakeway Dr, College Station, TX 77845-4512.

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