PT Classroom - Update in Balance Therapy for Patients After a Cerebrovascular Accident: Assessment and Retraining ׀ by Katie Nitsch-Pachniak, DPT, Elizabeth Alfonsi, DPT, Andrew Hajduk, DPT, Michael Scales, DPT, Gena Staniszewski, DPT

According to O’Sullivan, a stroke or cerebral vascular accident (CVA) is defined as a sudden loss of neurological function caused by an interruption in blood flow to the brain with neurologic deficits persisting for greater than 24 hours. Strokes cause damage to brain tissue. Clinical manifestations include changes in consciousness and impairments in sensation, motor function, cognition, perception, and language (1).

Strokes are the most common cause of disability among adults in the United States and affect approximately 700,000 individuals every year (1). Following stroke, patients often have disturbed balance and postural control leading to impairments in steadiness, symmetry, and dynamic stability. This can cause problems in reactive postural control and anticipatory postural control alike. The disruptions of central sensorimotor processing make it difficult to adapt postural movements to the changing demands of a task or environment. Patients’ responses to destabilizing forces are frequently insufficient and result in loss of balance and falls (1).

In fact, stroke is one of the greatest risk factors for falls in elderly people. Incidence rates of falls have been reported between 23% and 50% in studies of people with chronic stroke (>6 months post-stroke) in comparison to only an 11%-30% incidence rate reported for older community-dwelling adults who do not have a history of stroke. Up to 28% of people with chronic stroke who experience a fall report sustaining an injury as a result of the fall (2).

After having a stroke, patients typically undergo a substantial amount of rehabilitation to decrease impairments and regain function. One of the many focuses of physical therapy is improving balance in attempt to reduce the risk and incidence of falls. Physical therapy interventions to improve balance may include what are considered “traditional interventions” (i.e. neuromuscular facilitation, stretching and strengthening exercises, weight-bearing or shifting activities, exercises on rocker-boards, progressive challenges in stance, and ADL training) or the use of computer dynamic posturography (CDP). The SMART EquiTest Balance Master is one specific CDP machine and will be examined in this article.

In order to reduce the incidence and risk of falls and promote safety in patients following a CVA, it is important for physical therapists to be informed on what intervention is most effective in improving balance. Therefore, the purpose of this article is to examine whether the Balance Master is more effective than traditional physical therapy interventions in improving balance in individuals post-stroke who are at risk for falls.

SMART Balance Master
The SMART Balance Master, is a product of NeuroCom International Inc. The system is comprised of an 18” x 18” dual force plate that has rotation & translation capabilities to measure the vertical forces exerted by the user’s feet. The force plate is contained in a moveable visual surround. The system incorporates all three components of computerized dynamic posturography: sensory, motor, and central adaptation, and has both assessment & retraining capabilities (3).

The assessment protocols consist of the Sensory Organization Test (SOT), the Adaptation Test (ADT), and the Motor Control Test (MCT) (4). The SOT can be used to identify the primary system of balance impairment: somatosensory, vestibular, or visual. During this test, six different stages are performed. Each stage isolates and tests a particular sensory component of balance. Results from the stages can be found in a printable version of the “Equilibrium Score” graph. The amount of bars under each number on the x-axis represents the number of trials the participant performed in each stage of the test. A green bar signifies that a trial was successfully completed at or above the average COG stability for the participants’ age, sex, height, and weight. A red bar signifies that the trial was below average or that a fall occurred during the trial. A fall consists of taking a step, touching the walls of the Balance Master, or needing assistance from the physical therapist. The “Composite” score of the “Equilibrium Score” averages the results from the six stages and determines if the patient is above or below the average balance scores for persons of their age and anthropometrics. The “Sensory Analysis” graph illustrates the results from the “Equilibrium Score” in terms of the primary sensory system of balance utilized from the perspective stages of the test and compares the results to the norm. A red bar in this graph states that there is a particular sensory deficiency with this patient but does not diagnose the deficiency or state exactly where it is located. The “Strategy Analysis” and “COG Alignment” in the figure demonstrate what average percentage of balance was due to hip/ankle strategy and where the participants’ average COG alignment was during the six stages (5). (Click on image for a larger view)

The Balance Master also determines effectiveness of balance during unexpected movement of the patient’s surroundings. It does this through the mobile force plate. During this test, known as the Adaptation Test, the force plate will move suddenly to create dorsiflexion or plantar flexion at the ankle and the patient will need to use ankle, and potentially hip, strategies to maintain balance. The force plate is able to gather relevant information about the amount of ankle force that the patient uses to maintain balance, as well as the amount of postural sway the patient exhibits due to the perturbation. These findings can be available in a printable format as seen here. Like the graphic representation of the SOT, green figures in the Adaptation Test represent successful completions of the trial whereas red signify a fall. The vertical axis of the top two graphs represents ankle force while the horizontal axis depicts the trial number. The line graphs in the middle and on the bottom of the figure illustrate the movement of the participant’s center of gravity along with the direction in which the ankle force was generated during testing (6). (Click on image for a larger view)

Tests within the MCT protocol of the Balance Master include limit of stability, unilateral stance, weight bearing squat, and weight-shift tests. The results of each assessment protocol, SOT, ADT, and MCT, provide objective data which can be referred back to at a later date to determine balance improvement. These results can also provide objective data, upon which physical therapy goals and treatment ideas can be established. Using these assessment protocols, the Balance Master has been found to be reliable and valid in the assessment of dynamic balance in stroke patients (7).

The retraining capability of the Balance Master uses functional training exercises along with sensitive, real time visual feedback of movement. The clinician is able to adjust the proprioceptive/sensory-motor and visual training by changing the movement of the support surface, visual surround, or both to one of three settings: responsive, variably responsive, or random. In the responsive setting, the support surface or visual surround move in response to movement of the patient. The degree of movement of the support surface or visual surround in the variably responsive setting varies each time the patient moves. In the random setting, the movement of the support surface and visual surround is determined by the computer and is not in response to movement of the patient. The degree of movement is completely random (3).


Balance Master as the Gold Standard
The Balance Master stands at the forefront of current research. It has been used as the standardized assessment of balance in the study of fall prediction in the elderly (8), the effect of AFOs on balance (9), the effect of exercise on knee proprioception (10), the relationship between gait and balance in people with Parkinson’s disease (11), and the assessment of balance in people with chronic stroke. These studies, along with others, utilize the Balance Master as the “gold standard” of balance assessment. But, use of the Balance Master extends beyond research and is integrated within the hospital and clinical settings for those that have the financial means to invest in the system. In fact, the NeuroCom systems are used in 14 of the 17 “Honor Roll” hospitals in the United States according to U.S. News & World Report, Best Hospitals 2007 (12). This is likely due to versatility and comprehensive objective data collection as well as the reliability, responsiveness, and predictive validity that the Balance Master provides. According to a study of chronic stroke patients by Chein (13), the equilibrium score (part of the SOT) and the limits of stability test of the Balance Master had moderate to high reliability, acceptable responsiveness, and substantial predictive validity of ADL function. The only aspect of the Balance Master that did not support its use, according to Chien (13), was the inconsistent reliability, responsiveness, and predictive variability scores of the weight-shifting tests.

We have chosen to focus this article specifically on the Balance Master because it is the gold standard of CDP. Although, the Balance Master has been well studied in its ability to assess balance, its ability in retraining balance, specifically in patients post-CVA, has not received as much publicity. The remainder of this article will focus on the literature that has emerged regarding the training capabilities of the Balance Master, and whether it is more effective than conventional therapy in retraining balance and decreasing falls during stroke rehabilitation.

Retraining Capabilities of the Balance Master
The literature reviewed showed that although training with the Balance Master did improve both static and dynamic balance, the results were not significantly better than those who received conventional physical therapy. In the articles, static stability/balance was always tested in a variety of conditions. The conditions were static stance with eyes open, eyes closed, sway vision, and sway surface. Pso-Tsai Cheng et al found an improvement of maximal stability when comparing a Balance Master group to a control group. However, this difference was not statistically significant (14). In another clinical update, Deborah Nichols found that for static stability, biofeedback protocols such as the Balance Master “may not be any more beneficial than traditional approaches in increasing postural steadiness, but may add variability of practice to treatment sessions (15).” Walker et al found that using the Balance Master did improve patients’ static balance, however, not any more than the other groups that received physical therapy, or physical therapy and balance training (16). Finally, Chang Gung found that the trained group had improvements in static stability at the 6 month follow-up. At the follow-up, the patients were able to use more ankle strategies, and the amount of displacement of center of gravity decreased when compared to the control group. However, as in the other studies, there was no statistically significant difference (17).

In the articles, dynamic balance was seen to improve, though not always more than the control groups. Dynamic balance was usually measured by examining how close patients could get to their limits of stability (LOS), as well as how fast they could move from one target to another. Gung found significant improvements in dynamic balance at the 6 month follow up. Patients had an increased axis velocity from 3.25 degrees/second to 4.11 degrees/second. Patients were able to get closer to their LOS and had better directional control. Pao-Tsai Cheng et al also agreed with this conclusion. This group found significantly improved dynamic balance at initial training and at the 6 month follow-up. For on-axis velocity, the training group increased from 3.19 degrees/second to 4.08 degrees/second at the end of treatment, and to 4.11 degrees/second at the 6 month follow up (14). Walker et al found improvement in dynamic balance, but at the same rate as the control group. They state that it is “conceivable that the regular therapy sessions alone sufficed to enable patients to maximize their potential (16).” Additionally, the visual feedback provides patients with constant feedback. While this feedback may be beneficial during training, patients may become too dependent on it, and lose their ability to self-correct when the visual feedback is not available. Nichols found that weight-shifting tasks that can be performed on the Balance Master improved “accuracy of weight shift” in a variety of subjects, including older subjects with and without balance issues as well as subjects with hemiparesis (15). However, Nichols does note that “in cases where feedback training and testing protocol [are] similar, the ability to distinguish between performance and learning was limited (16).”

In addition to looking at static and dynamic balance, several of the studies also looked at outcome measurements, which overall did not show improvements between groups. Using the FIM, Gung looked at mean changes of self-care, sphincter control, locomotion and mobility functions. Gung identified that there was improvement in all these areas, but only self-care had statistically significant difference at the 6 month follow up. The authors also noted that using the Balance Master “seemed to be more correlated with the ability to perform self-care tasks than locomotion and mobility function (17).” Walker et al looked at balance based on activity type. The three tests used were the Berg, the Timed “Up and Go” test (TUG test), and gait speed. While the authors did find improvements in all their scores, there were no differences between the three groups for any outcome measure overtime. This indicates equivalency in balance performance regardless of differences in intervention. Walker notes that all gains were greatest during the inpatient period and that standard treatment along with spontaneous recovery may be enough to maximize patients’ potential (16). Finally, a randomized control trial by Greiger et al examined training with the Balance Master in addition to conventional physical therapy to improve balance and mobility as measured by the Berg Balance Scale and the Timed “Up and Go” Test. When compared to a control group receiving conventional physical therapy, the addition of training with visual biofeedback and a forceplate system (e.g. Balance Master) resulted in no differences between the groups after 4 weeks of intervention. However, the mean difference scores for the entire population of the study did not correlate to each other. This suggests that some subjects made greater gains on one measure than on the other. Furthermore, the study may have had a type II error as it only contained 13 subjects (18).

The majority of the articles reviewed did not directly study whether there was a difference in the incidence of falls between the Balance Master groups and the control groups. However, some theorized that there would be a decrease in the risk of falls if there were improvements in other tasks. Gung states that using the weight-shifting tasks done in their study may be helpful in improving stance symmetry, but did not relate it to better gait or other high level balance or mobility tasks (17). Nichols et al found that by using the Balance Master, subjects were able to expand their limits of stability. In theory, Nichols believes this should decrease the likelihood of falling, but at the time of their study this relationship had not been examined (15). One article that did look at the occurrence of falls was that by Pao-Tsai Chung et al. This group relied on self-reporting from patients at the 6 month follow up. The group found that the occurrence of falls in the training group was lower than that of the non-trained group (17.8% vs. 41.7%). However, this difference was not statistically significant. The authors feel this may be a result of a small sample size (14).

Conclusion
Balance disturbances are one of the biggest issues that stroke patients deal with, in turn it is essential to determine the best form of evaluation and treatment for these same individuals (1). Recent studies show that NeuroCom’s Balance Master is currently the gold standard for assessment of balance, especially in individuals who have had a CVA. The Balance Master provides objective data allowing clinicians to document and making it easier for these clinicians to show improvement in patients. The Balance Master is also being used for retraining after strokes in order to improve static and dynamic balance, improve gait, and decrease the risk of falls. Recent study results have shown that using a balance master during therapy is no more beneficial than standard post-stroke rehabilitation when looking at a patient’s improvements in balance. Across the board, studies found that there is generally an improvement in balance after training, but it is not a statistically significant difference when comparing to a control group who receives the traditional therapy.

Many major hospitals in the United States have instituted the use of the Balance Master in agreement with the fact that studies have shown that it is currently the gold standard for balance assessment. Further testing is necessary however, to determine if the Balance Master is any better than conventional physical therapy after stroke for improving balance and gait or decreasing the risk of falls. At this time, study results show no significant difference between conventional PT and using the Balance Master when it comes to balance improvements post-stroke.