Medical Policy: 02.01.08
Original Effective Date: December 2000
Reviewed: July 2018
Revised: July 2018
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This Medical Policy document describes the status of medical technology at the time the document was developed. Since that time, new technology may have emerged or new medical literature may have been published. This Medical Policy will be reviewed regularly and be updated as scientific and medical literature becomes available.
Dynamic posturography, also known as computerized dynamic posturography (CDP), tests a patient's balance control in situations intended to isolate factors that affect balance in everyday experiences. Posturography provides quantitative information on the degree of imbalance present but is not intended to diagnosis specific types of balance disorders.
Complaints of imbalance are common in older adults and contribute to the risk of falling in this population, and are a cause of death and disability in this population in the United States. Maintenance of balance is a complex physiologic process, requiring interaction of the vestibular, visual and proprioceptive/somatosensory system, and central reflex mechanisms. Balance is also influenced by the general health of the patient (i.e. muscle tone, strength, range of motion). Therefore, identifying and treating the underlying balance disorder can be difficult. Commonly used balance function tests (e.g. electronystagmography, rotational chair tests) attempt to measure the extent and site of a vestibular lesion but do not assess the functional ability to maintain balance.
Dynamic posturography aims to provide quantitative information on a patient’s functional ability to maintain balance. The patient, wearing a harness to prevent falls, stands on an enclosed platform surrounded by a visual field. By altering the angle of the platform or shifting the visual field, the test assesses movement coordination and the sensory organization of visual, somatosensory, and vestibular information relevant to postural control. The patient undergoes 6 different testing situations designed to evaluate the vestibular, visual and proprioceptive/somatosensory components of balance. In general terms, the test measures an individual’s balance (as measured by a force platform to calculate the movement of the patient’s center of mass) while visual and somatosensory cues are altered. These tests vary by whether eyes are open or closed, the platform is fixed or sway-referenced, and whether the visual surround is fixed or sway-referenced. Sway-referencing involves making instantaneous computer-aided alterations to the platform or visual surround to coincide with changes in body position produced by sway. The purpose of sway-referencing is to cancel out accurate feedback from somatosensory or visual systems that are normally involved in maintaining balance. In the first 3 components of the test, the support surface is stable, and visual cues are either present, absent or sway-referenced. In tests 4 to 6, the support surface is sway-referenced to the individual, and visual cues are either present, absent or sway-referenced. In tests 5 and 6, the only accurate sensory cues available for balance are vestibular cues. Results of computerized dynamic posturography have been used to determine what type of information (i.e., visual, vestibular, proprioceptive) can and cannot be used to maintain balance. Computerized dynamic posturography cannot diagnose pathology or be used to localize the site of a lesion.
Posturography tests a patient’s balance control in situations intended to isolate factors that affect balance in everyday experiences. Balance can be rapidly assessed qualitatively by asking the patient to maintain a steady stance on a flat or compressible surface (i.e foam pads) with the eyes open or closed. By closing the eyes, the visual input into balance is eliminated. Use of foam pads eliminates the sensory and proprioceptive cues. Therefore, only vestibular input is available when standing on a foam pad with eyes closed.
The purpose of computerized dynamic posturography in patients who have balance dysfunction is to inform a decision whether to pursue additional diagnostic workup (e.g. imaging studies that would not have been indicated based on clinical presentation alone) or immediate treatment.
The relevant population(s) of interest are patients presenting with balance dysfunction or dizziness. It would be expected that these patients will have had an initial basic evaluation directed by symptoms that will have included a clinical examination and history, with appropriate vital signs and orthostatic blood pressure measurements, and may have had basic evaluations as directed by their symptoms (e.g. electrocardiogram).
Depending on the clinical presentation, patients with balance dysfunction may be managed with clinical evaluation alone or with more intensive evaluations including vestibular functioning testing, which can be used to localize the cause of the dysfunction. The ultimate goal of evaluation is to correctly diagnose and treat the underlying condition.
Patients with balance dysfunction being evaluated with computerized dynamic posturography are generally seen in the outpatient setting. Testing may be conducted by audiologists, physical therapists, or technologists under the supervision of physicians.
A test must detect the presence or absence of a condition, the risk of developing a condition in the future, or treatment response (beneficial or adverse).
No studies were identified that evaluated the sensitivity and specificity of dynamic posturography for diagnosing any specific balance disorder compared with commonly accepted balance tests. There is no criterion standard test for measuring balance, which is a physiologic parameter. Absent a criterion standard comparison; the literature search sought to identify studies that systematically compared results of dynamic posturography and other balance tests in an appropriate patient population (i.e., individuals at increased risk of falling due to balance issues).
Several studies have used both dynamic posturography and another test to assess balance. For example, Fritz et. al. (2015) assessed the correlation between dynamic and static posturography and other measures of gait and balance dysfunction in 57 ambulatory patients with multiple sclerosis. Two dynamic posturography parameters and 4 static posturography parameters were measured. Walking velocity (the alternative test) was measured in 2 ways: (1) in a laboratory using the Optotrak Motion Capture System and (2) using the timed 25-foot walk test. In regression analysis, demographics, one of the dynamic posturography parameters (anteroposterior sway), and one of the static posturography parameters (eyes open, feet apart) explained 95.3% of the variance in walking velocity. A higher degree of anteroposterior sway, assessed using dynamic posturography, was significantly associated with higher walking velocity. Although the study found that dynamic posturography was associated with measures of walking velocity, the utility of this information regarding impact on patient management is uncertain.
A study by Ferrazzoli et. al. (2015) compared dynamic posturography with the Berg Balance Scale score. The Berg Balance Scale is a 14-item tool that assesses performance on a variety of functional tasks, each rated 0-to-4 (maximal score, 56 points). Lower scores indicate higher fall risk. The study included 29 patients with Parkinson disease (PD) not complaining of balance problems and 12 healthy controls matched for age and sex. Scores on the Berg Balance Scale were significantly lower in PD patients than in controls (p=0.002). Similarly, results of body sway analysis assessed by posturography differed significantly between PD patients and controls. Specifically, compared with controls, PD patients had a higher standard deviation of body sway measurements in the eyes open (p=0.005) and in the eyes open counting (p=0.020) conditions. The standard deviation of PD patients was also higher than controls in posturography along the mediolateral axis in the eyes open condition (p=0.019), but results were similar in the eyes open counting condition. The authors suggested that posturography could be used to identify early balance disorders in PD patients before they develop clinical symptoms, and that rehabilitation programs could be developed to address specific balance issues. As discussed in the next section, there is a lack of prospective studies comparing health outcomes in patients managed with and without dynamic posturography.
Other published literature on dynamic posturography has assessed fall risk in older individuals and other populations. For example, Whitney et al (2006) retrospectively reviewed 100 charts of individuals referred to a balance and falls clinic with a vestibular diagnosis using dynamic posturography. Patients who reported multiple falls over 6 months had lower initial scores on the Sensory Organization Test than those who reported one or no falls.
Additional studies have used dynamic posturography as a research tool to study balance (eg, in older adults, PD patients, knee osteoarthritis patients); these studies were not designed to evaluate the clinical validity of dynamic posturography. Dynamic posturography has also been considered a control technique in studies evaluating other novel methods of assessing balance. For example, Alahmari et. al. (2014) assessed the reliability and validity of a balance rehabilitation device and compared findings with dynamic posturography using the EquiTest.
Describing the diagnostic performance of dynamic posturography in terms of sensitivity and specificity is difficult given the lack of a true criterion standard for measuring balance. The available studies comparing dynamic posturography with other types of clinical measures of balance have suggested that posturography results correlate with those measures; however, whether dynamic posturography can be used as a diagnostic test is unknown.
A test is clinically useful if the use of the results informs management decisions that improve the net health outcome of care. The net health outcome can be improved if patients receive correct therapy, or more effective therapy, or avoid unnecessary therapy, or avoid unnecessary testing.
Direct evidence of clinical utility is provided by studies that have compared health outcomes for patients managed with and without the test. Because these are intervention studies, the preferred evidence would be from randomized controlled trials.
No randomized or nonrandomized controlled studies were identified that compared health outcomes in patients when treatment decisions were made with and without the results of dynamic posturography.
Direct evidence of how dynamic posturography can be used to improve outcomes is lacking. Absent direct evidence for a diagnostic test, a chain of evidence can sometimes be identified to demonstrate improvement in health outcomes. However, in the case of dynamic posturography, the chain of evidence about clinical validity and how the test would be used in practice is uncertain; therefore, no inferences can be made about clinical utility.
For individuals with suspected balance disorders who receive dynamic posturography, the evidence includes cross-sectional comparisons of results in patients with balance disorders and healthy controls, and retrospective case series reporting outcomes for patients assessed with dynamic posturography as part of clinical care. There are no generally accepted reference standards for dynamic posturography, which makes it difficult to determine how the results can be applied in clinical care. There is a lack of well-designed, randomized controlled trials (RCTs) with blinded assessments to demonstrate diagnostic utility of dynamic posturography compared with standard tests. Furthermore, there is insufficient evidence demonstrating consistent and beneficial effects of dynamic posturography testing on patient-relevant outcomes. The evidence is insufficient to determine the effects of this technology on net health outcomes.
The American Academy of Otolaryngology – Head and Neck Surgery have issued a position statement and a guideline that mention dynamic posturography:
The NeuroCom EquiTest® is a dynamic posturography device that received 510(k) marketing clearance from the U.S. Food and Drug Administration (FDA). Other dynamic posturography device makers include Micromedical Technology, Metitur, and Vestibular Technologies.
Dynamic Posturography is considered investigational for all indications.
Overall, there is weak evidence in the peer-reviewed literature regarding the efficacy of dynamic prosturography for evaluating vestibular and other disorders. There is a lack of well-designed, randomized controlled trials (RCTs) with blinded assessments to demonstrate the diagnostic utility of dynamic posturography compared with standard tests. Furthermore, there is insufficient evidence demonstrating consistent and beneficial effects of dynamic posturography testing on patient-relevant outcomes. The evidence is insufficient to determine the effects of this technology on net health outcomes.
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