Brain injury is a major cause of disability in the United States. Approximately 175 to 200 persons per 100,000 in the United States are admitted to hospitals with brain trauma each year, while 5.3 million Americans live with brain injury at a cost of $48.3 billion annually. The peak incidence occurs among young adults between the ages of 15 and 24 years and accounts for approximately 500,000 new cases per year with at least twice as many men as women being affected. Residual disability from brain injury varies according to the severity of injury. Approximately 80% of all people with brain injury have mild trauma, 10% have moderate injuries, and 10% have severe injuries. Research indicates that 10% of those persons with mild brain injuries and 100% of those with severe brain injuries will have a residual disability. Approximately 99,000 people with brain injury live with permanent disability1,2 and the numbers who survive are increasing yearly.2
Impaired postural control, the ability to maintain the center of mass over the base of support during static and dynamic balance tasks, is a common sequelae postbrain injury. It results from damage to the neuronal pathways that process vestibular, visual and proprioceptive inputs, and motor control responses. Individuals who sustain neurological damage may have problems in maintaining dynamic balance during functional activities such as transfers and walking.3 Balance impairments can lead to serious long-term disability and safety concerns such as falls. Therefore, physical therapists must be able to reliably assess postural control in persons with brain injury.
Many tools have been developed to accurately assess balance in clinical settings; however, none are specifically designed for examination of persons with brain injury. One reliable and valid performance-based functional measurement test is the Berg Balance Scale (BBS)4–7 that addresses various static and dynamic functional capabilities in sitting and standing. Although originally developed with older adults in mind, Berg has suggested that this tool may be beneficial for other populations with balance deficits.5,7 When using the BBS the person is asked to perform 14 various functional activities such as sit to stand, standing unsupported, reaching forward with an outstretched arm, turning 360°, and alternate stepping in succession onto an 8-inch platform. The individual is scored using a 5-point ordinal scale, 0 to 4, on the basis of ability to perform and maintain the functional task. Scores on the BBS have been correlated with both computerized platform measures (r = −0.55) and caregiver reports of performance (r = 0.56) in older adults.4,5 The BBS was found to have excellent interrater (ICC = 0.98) and intrarater reliability (ICC = 0.98), and good predictive validity for falls in an elderly population.4–7 The BBS also has been studied in persons after stroke5,7,8 and was shown to be useful in the first 90 days poststroke; but the BBS demonstrated a ceiling effect during the 90- to 120-day period.8
Other performance-based tests are also available that examine sensory and motor strategies related to balance. These tests are measured using time in standing, loss of balance, and sway. As with the BBS, most of these tests have been evaluated for use in older adults. The Romberg and Sharpened Rhomberg are examples of such tests.9–12 The Romberg measures static standing balance for approximately 30 seconds manipulating vision. The Sharpened Romberg similarly measures maintenance of static balance while manipulating vision. In both tests an increased sway is often observed for individuals with neurological dysfunction or older adults, especially with eyes closed. The Clinical Test for Sensory Interaction of Balance (CTSIB) is a more complex sensory strategy balance test. It is administered by manipulating the support surface (ie, firm vs foam), visual conditions (ie, eyes open, eyes closed), and vestibular system (sway reference), while an individual is asked to maintain their standing balance. The CTSIB test helps determine which sensory system (visual, haptic, or vestibular) the person relies on to maintain balance.13 Although easily administered in the clinic, these tests do not quantify sway characteristics.4,7 Suggestions to quantify sway in the CTSIB have been proposed by Horak and Shumway Cook.13 Static balance tests can be performed on various types of stable force platforms to obtain objective measures of total anteropos-terior and mediolateral postural sway.3,4,7,14–17 Reviews of other balance performance-based measures not mentioned here have been previously published.18,19
Computerized systems have been developed to assess dynamic stability as a way to measure balance in clinical or research settings.20,21 Nashner and colleagues created a balance platform that provides similar information to the CTSIB by determining the role of each sensory system in balance responses.22 It is an automated standing platform in which the support surface and visual surround move to challenge balance responses. It requires that the individual differentiate between altered and appropriate sensory input and select an appropriate movement pattern to maintain balance.22–24 The Balance Master Limits of Stability Test (BMLOST) was developed in an effort to quantify the information obtained from clinical performance measures in the hope of reliably assessing static postural sway, dynamic weight shift, and dynamic limits of stability on a stable plat-form.22,25,26 A person's balance is challenged with increasing difficulty under various task conditions (ie, static eyes open and eyes closed, weight shift forward and backward, weight shift right and left, and weight shifting to various targets at specified limits of stability in the north, northeast, east, southeast, south, southwest, west, and northwest directions as illustrated in Figure 1). The BMLOST has been explored in various patient populations, but few studies investigated the usefulness in persons with brain injury.17,23,24
The BBS and BMLOST tests are used often in clinical practice. Both tools test static and dynamic balance, but do not involve a walking component and have shown good reliability in other populations. The BBS examines balance at a task level whereas the BMLOST examines balance at a strategy level. Therefore clinicians may choose to combine the tests in a comprehensive analysis of balance. Neither test has been shown to be reliable for individual's postbrain injury. Therefore we sought to determine the test-retest reliability of the BBS and BMLOST. Based on the reported reliability for these tests in other populations, we hypothesized that both tests would demonstrate good reliability.4,8,25,26
Five participants between the ages of 20 and 32 (Mean = 24.4 ± 5. 3) were recruited from a transitional living community in Galveston, Texas (Table 1). This sample of convenience included 1 woman and 4 men. Each participant had a Rancho score of VI or more (confused appropriate) and were able to: (1) understand simple commands, and (2) stand and walk independently with or without an assistive or orthotic device. Information was given to each individual about the study and informed consent was obtained prior to participation. University and facility Institutional Review Boards approved the study.
Testing was completed using the BBS and BMLOST (version 3. 4) to include eyes open, eyes closed, center target eyes open, rhythmic weight shift (at slow, medium, and fast speeds of 3, 2, and 1 seconds), followed by 75% limits of stability testing (clockwise) on the same day. The 75% LOS test (Figure 1) is the theoretical percent each participant would be required to move the center of mass as represented by a cursor on a screen from a center to a perimeter target and back, representing the outer limits (N, NE, SE, S, SW, W, NW). The 75% LOS test was selected because of its dynamic nature to determine the person's ability to weight shift in 8 different directions around a mid-point without loss of balance. A test-retest reliability study of the BBS and the BMLOST was performed within a week of initial testing. Two examiners, third year physical therapy students under the supervision of a licensed physical therapist with over 30 year's experience, performed the testing. Both students were educated to perform the testing on 4 different sessions. One student performed the BBS and the second student completed the BMLOST. The same person performed testing for either the BBS or BMLOST, and was blinded to the repeat test results.
All participants were evaluated using the BBS and the BMLOST. Prior to performing each test, each participant was given similar, standard verbal instructions. A 5-minute warm-up period was allowed on the BMLOST prior to testing to familiarize the individual with the instrument. All participants were given a second attempt at each test and the best score was recorded. Testing was performed in a random sequence starting with the BBS or the BMLOST first, and then completed the other test immediately after a 5-minute rest. We were unable to control for times of day for testing, medications, and activity level. During the study, all participants wore comfortable shoes and any orthotic devices that were normally used for walking.
During the BBS testing, the participant performed the 14 tasks according to the standard procedures described on the testing form.6 An ordinal score, 0 to 4, was given for each item on the BBS based on the descriptions for each item provided, and a total score was tallied at the end of the evaluation period. The testing took approximately 20 minutes to perform. The BMLOST25 was performed beginning with static standing on the stationary force platform with eyes open (EO), eyes closed (EC), and target with eyes open. Next, active, dynamic weight shifting was conducted at 3 speeds—slow, medium, and fast—between 2 medial/lateral (ML), then 2 forward/backward (FB) targets and scored as percentage of limits of stability (% success of reaching a set theoretical target with minimal deviation or extraneous movement).25 The limits of stability test (75% LOS) with eyes open followed. Participants were allowed to watch the screen while performing the test. Movement time between targets (MT; total time to complete the weight shift between center target and 8 perimeter targets in seconds), path sway (PS; total % LOS path length summed over 8 targets), and distance errors (DE; total % LOS deviation of path length between center and outer target summed over 8 targets) were recorded for each participant. Three out of 5 participants had difficulty completing the dynamic weight shift test at faster speeds of 1 and 2 seconds and therefore performed them at 3-second intervals. The BMLOST took approximately 30 minutes to perform.
The SPSS 11.3 statistical software was used to calculate the test-retest reliability between participants' scores obtained from all tests at the 0.05 alpha level. Data from the test-retest reliability study (N = 5) were analyzed using an Intraclass Correlation Coefficient (ICC2,1).26
The mean (SD), range (minimum and maximum values), and coefficient of variation (CV) for each balance test for the 5 participants for both first and second trials combined are presented in Table 2. No order effects of testing were found between the BBS and BMLOST using independent 2-tailed t-test analyses. None of the participants had previously been exposed to either test.
Test-retest reliability testing (N=5) for the Berg Balance Scale and Balance Master are shown in Table 3. The Berg Balance Scale demonstrated excellent reliability (ICC2,1 = 0.986).26 Reliability of the Balance Master was moderate to good for static eyes open (ICC2,1 = 0.840) and eyes open with target (ICC2,1 = 0.953). Moderate reliability was found for dynamic limits of stability (75%) movement time (ICC2,1 = 0.825) and path sway (ICC2,1 = 0.846), but was low for distance error (ICC2,1 = 0.632). Reliability was poor for the forward (ICC2,1 = 0.228) and medial lateral weight shift (ICC2,1 = 0.281).
Average absolute difference between test 1 and test 2 for the BBS was 1. 4. For the BMLOST static measures (% maximum area), the average absolute differences were 0.12 for eyes open,0.51 for eyes closed, and 0.05 for eyes open with a target. Dynamic measures of weight shift (% LOS) for the 3-second condition were 12.16 for medial/lateral and 11.27 for forward/backward. Differences for the 2 and 1 second conditions are not reported since not all participants were able to successfully complete the tests/tasks. Lastly, the average absolute differences for the mean 75% limits of stability measures were 0.67 for movement time (s), 21.68 for path sway (% LOS), and 2.33 for distance error (% LOS).
Test-retest reliability of the BBS was found to be excel-lent. These findings are similar to those reported for older adults (ICC2,1 = 0.98)4,5 and in persons poststroke (ICC2,1 = 0.98).27 There was only a 1. 4 absolute change in the test score, most of which was accounted for by participant #4 who had the most change in absolute score (4 points) from test 1 to test 2 for the BBS which is likely related to her seizure activity between testing sessions with subsequent reports of drowsiness and dizziness. This small absolute change would not confound the 5 to 7 point change in the BBS score which is interpreted as a clinically meaningful change in persons after stroke.28 However, because of our small sample size we consider these preliminary results and further testing is needed to confirm these findings.
In the sample of patients tested for this study 2 of the 5 individuals had a very high BBS scores suggesting a possible ceiling effect. As the BBS does not address walking, other performance-based tools such as the Dynamic Gait Index (DGI)29 and Functional Gait Assessment (FGA)30 could be considered for this population. These 2 tools include walk-ing, head turning, and stair climbing tasks as important components of dynamic balance testing, and could be considered higher-level balance tests relative to the BBS.
Reliability for the BMLOST ranged from poor to good. Static measures (eyes open with and without a target), movement time, and path sway had moderate to good test-retest reliability, while weight shift had poor reliability. Liston and Brouwer27 studied the test-retest reliability of the BMLOST for persons poststroke without previous exposure to the BMLOST. Their results indicated that movement path (path sway; ICC = 0.84) and movement time (ICC = 0.88) when tested within a week apart were moderately reliable. The results compare favorably with the persons with BI in our study for total scores of movement time (ICC2,1 = 0.825) and path sway (ICC2,1 = 0.845), but we found distance error was less reliable. The poor reliability for the weight shift might be explained by the individual's asymmetrical starting position. As they were biased in their posture towards one direction of the shift, it was more difficult; and in some cases, not possible for them to shift to one side when there was a time constraint. Perhaps this time constraint partially explained the production of a more erratic pattern.
Although BMLOST is a widely used measurement for bal-ance,25,27,31,32 participants are required to perform activities while standing on the force plates that they may rarely perform on a daily basis. Tasks such as the BMLOST (75%) require static upright balance or weight shifting between a center point and 8 different targets in a closed environment within a specified time period, as well as concentration, attention span, and visual perceptual abilities, which are substrates for more ecological valid balance tasks. The moderate to good reliability of the static measures and movement time, may recommend these aspects of the BMLOST to give clinicians baseline data about individual balance strategies. It also may assist with dissecting an individuals' use of the cognitive, visual, somatosensory, and muscu-loskeletal aspects of balance.
We were not able to control for participant's type of injury or area of the brain affected, activity level, medica-tions, distractions, or fluctuations in mood or periods of irritability, which may have been a source of variance unrelated to the test procedures. Variability in performance between participants, as noted by coefficient of variation, though, was relatively low for the BBS (CV = 0.26) in comparison with higher values for the BMLOST (CV range = 0.20 to 0.89). The individuals that scored the test were physical therapy students who had classroom and clinical educational training in use of both the BBS and BMLOST suggesting that the findings could be generalized to more experienced therapists that receive similar training with test administration
Clinically, this preliminary study suggests that both measures can be reliably used in a select population of persons with brain injury. A clinician may select and reliably use a performance-based tool, such as the BBS, in conjunction with or separate from the computerized BMLOST, to determine the balance capability of an individual with brain injury.
Test-retest reliability was examined in a group of individual's postbrain injury. Excellent reliability was found for the BBS and poor to good reliability was found for the BMLOST. As the sample size used in this study was small, these preliminary findings are more robust for the BBS and the reliability of the BMLOST may require additional testing.
Our thanks to the all the participants and to Douglas Murphy, PhD for his assistance in statistical analyses.
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