Vestibular evaluation--electronystagmography, rotational testing, and posturography

Clinical usefulness of the rotatory, caloric, and vestibular evoked myogenic potential test in unilateral peripheral vestibular pathologies

OBJECTIVE

The aim of this study was to investigate the diagnostic capacity of three different rotatory tests, and to investigate the clinical effectiveness of the caloric, rotatory, and vestibular evoked myogenic potential (VEMP) test.

DESIGN AND STUDY SAMPLE

Several rotatory tests--sinusoidal harmonic acceleration test (SHAT), pseudorandom rotation test (PRRT), velocity step test (VST)--and a caloric and a VEMP test, were given to 77 patients (mean age 52 years) with a unilateral peripheral vestibular pathology, and 80 control subjects (mean age 48 years).

RESULTS

For the rotatory test, the highest diagnostic capacity was obtained with the 0.01 Hz SHAT frequency, followed by 0.1 and 0.05 Hz. A higher diagnostic accuracy was reached for the caloric and VEMP test. The caloric test demonstrated high sensitivity and specificity values, but the 0.01 Hz SHAT rotation appeared more sensitive, and the VEMP more specific, than the caloric test.

CONCLUSION

A selection of the 0.01, 0.05, and 0.1 Hz SHAT rotations is suggested as the most ideal rotatory test protocol, and a combination of rotatory, caloric, and VEMP testing will result in a more complete examination of our vestibular system.

Test order effects of computerized dynamic posturography and calorics

PURPOSE

To determine whether there is a test order effect of the caloric subtest of videonystagmography on the Sensory Organization Test (SOT) of computerized dynamic posturography, and to assess the learning effect of multiple posturography test sessions on the SOT score.

METHOD

Scores on the 6 SOT conditions before and after caloric testing were compared for 10 participants age 18-36 years. Four SOT sessions were completed prior to caloric testing to assess the presence of a learning effect and establish precaloric baseline SOT scores. All participants had normal vestibular systems with no history of dizziness or imbalance.

RESULTS

Caloric testing had a significant effect on the equilibrium score for only 1 of 6 test conditions. While meeting statistical significance, the actual change in score for this condition was very small. Equilibrium scores improved for the more difficult test conditions between the 1st and 2nd SOT sessions.

CONCLUSION

Results indicate that there are minimal test order effects of calorics on the SOT. Results confirm that a significant improvement in score for more challenging test conditions occurs between SOT Sessions 1 and 2 as a result of learning. Therefore, clinicians must be cautious when using posturography to monitor patient improvement.

Evaluation of subjectivity in the interpretation of videonystagmography

CONCLUSION

Subjectivity seems to play a definite role in the interpretation of the pendular test, but somewhat less for caloric testing, where pure visual analysis seems to be more reliable. Automated values provided by proof-tested software may be useful.

OBJECTIVES

In some centers, the interpretation of videonystagmography is still based on direct visual analysis of recorded tracings. Our study addresses the importance of subjectivity in the interpretation of videonystagmographic readings.

PATIENTS AND METHODS

Two experts (one junior and the other senior) were asked to interpret the same caloric and pendular tests on two different occasions, 3 months apart. Initial reading was performed without knowledge of the patient's history or the results of other neuro-otological tests. Three months later, interpretations were done with complete access to the patient's charts. The experts' answers were compared to the values provided by the computer software.

RESULTS

For the pendular test, inter-expert agreement was poor. With knowledge of the patient's history, the expert's interpretations tended to coincide with the software's calculations. For the caloric test, interpretation was less variable.

Stepping stability: effects of sensory perturbation

Background

Few tools exist for quantifying locomotor stability in balance impaired populations. The objective of this study was to develop and evaluate a technique for quantifying stability of stepping in healthy people and people with peripheral (vestibular hypofunction, VH) and central (cerebellar pathology, CB) balance dysfunction by means a sensory (auditory) perturbation test.

Methods

Balance impaired and healthy subjects performed a repeated bench stepping task. The perturbation was applied by suddenly changing the cadence of the metronome (100 beat/min to 80 beat/min) at a predetermined time (but unpredictable by the subject) during the trial. Perturbation response was quantified by computing the Euclidian distance, expressed as a fractional error, between the anterior-posterior center of gravity attractor trajectory before and after the perturbation was applied. The error immediately after the perturbation (Emax), error after recovery (Emin) and the recovery response (Edif) were documented for each participant, and groups were compared with ANOVA.

Results

Both balance impaired groups exhibited significantly higher Emax (p = .019) and Emin (p = .028) fractional errors compared to the healthy (HE) subjects, but there were no significant differences between CB and VH groups. Although response recovery was slower for CB and VH groups compared to the HE group, the difference was not significant (p = .051).

Conclusion

The findings suggest that individuals with balance impairment have reduced ability to stabilize locomotor patterns following perturbation, revealing the fragility of their impairment adaptations and compensations. These data suggest that auditory perturbations applied during a challenging stepping task may be useful for measuring rehabilitation outcomes.

Can Tai Chi improve vestibulopathic postural control?

OBJECTIVES

To evaluate the rationale and scientific support for Tai Chi as an intervention for vestibulopathy and to offer recommendations for future studies.

DATA SOURCES

A computer-aided search, including MEDLINE and Science Citation Index, to identify original Tai Chi studies published in English; relevant references cited in the retrieved articles were also included.

STUDY SELECTION

A preliminary screening selected all randomized controlled trials (RCTs), non-RCTs, case-control studies, and case series that included Tai Chi as an intervention and had at least 1 outcome variable relevant to postural stability.

DATA EXTRACTION

Authors critically reviewed studies and summarized study designs and outcomes in a summary table.

DATA SYNTHESIS

Twenty-four Tai Chi studies met screening criteria. No studies specifically studying Tai Chi for vestibulopathy were found. Collectively, the 24 studies provide sometimes contradictory but generally supportive evidence that Tai Chi may have beneficial effects for balance and postural impairments, especially those associated with aging. Ten RCTs were found, of which 8 provide support that Tai Chi practiced alone, or in combination with other therapies, can reduce risk of falls, and/or impact factors associated with postural control, including improved balance and dynamic stability, increased musculoskeletal strength and flexibility, improved performance of activities of daily living (ADLs), reduced fear of falling, and general improvement in psychologic well-being. Studies using other designs support the results observed in RCTs.

CONCLUSIONS

At present, few data exist to support the contention that Tai Chi specifically targets the impairments, functional limitations, disability, and quality of life associated with peripheral vestibulopathy. There are, however, compelling reasons to further investigate Tai Chi for vestibulopathy, in part because Tai Chi appears useful for a variety of nonvestibulopathy etiologic balance disorders, and is safe. Especially needed are studies that integrate measures of balance relevant to ADLs with other psychologic and cognitive measures; these might help identify specific mechanisms whereby Tai Chi can remedy balance disorders.

Kinetic analysis of planned gait termination in healthy subjects and patients with balance disorders

We examined the stability and strategies used by balance impaired (vestibular hypofunction, VH: n=25; cerebellar damage, CB: n=20) patients and healthy (HE: n=52) controls during planned gait termination. Upper body strategies (during final stride and final step) were investigated using peak positive kinetic power (KP((+)): kinetic energy increasing), and peak negative kinetic power (KP((-)): kinetic energy decreasing) of the head-arms-trunk segment. Compared to HE controls (P<0.05): CB patients' medio-lateral KP((+)) and KP((-)) and were 53 and 71% higher during final stride, respectively; VH patients medio-lateral KP((+)) and KP((-)) was 78 and 57% higher during final step, respectively, and; during the final, standing stage VH patients were 32% less stable (from phase plane analysis) in the frontal plane. The excessive energy transfers in final stride for CB patients was likely due to poor eccentric muscle control when preparing for the stop. VH patients had difficulty controlling lateral stability during final step and once they had stopped walking, probably due to the lack of vestibular feedback regarding forward velocity changes. A better understanding of these abnormal movement patterns or compensatory strategies may assist in rehabilitation of patients with balance dysfunction.

Vestibular rehabilitation: useful but not universally so

OBJECTIVE

Although vestibular rehabilitation (VR) is gaining popularity, few data support its utility in improving locomotor stability, and no good predictors exist of whom will benefit most.

STUDY DESIGN AND SETTING

A double-blind, placebo-controlled randomized trial of vestibular rehabilitation was conducted at a large tertiary care hospital on 124 patients (59 +/- 18 years old) with unilateral (n = 51) or bilateral (n = 73) vestibular hypofunction, of whom 86 completed a 12-week intervention. Of these 86, 27 returned for long-term (1-year) follow-up testing. The primary outcome measure was locomotor stability.

RESULTS

Group A (6 weeks of VR) significantly (P < 0.01) increased their gait velocity and stability compared with group B (6 weeks of strengthening exercise), but there was a smaller difference (P = 0.05) between groups at 12 weeks, when both had had VR; there were no group differences at 1 year. Of the 86 who completed the intervention, 52 (61%) had clear locomotor gains.

CONCLUSION AND SIGNIFICANCE

VR is helpful for most patients in providing locomotor stability, but further work is needed to determine the factors that prevent VR from being effective for all patients with vestibulopathy.

Testing the central vestibular functions: a clinical survey

In vestibular examinations anomalies in the saccade and smooth pursuit tests as well as the fixation suppression after caloric stimulation might indicate central lesions in the vestibular system. Additionally, a high gain in the torsion test is suspicious of cerebellar dysfunction. In this study, 141 patients out of 973 had at least one of these anomalies. For 125 patients we were able to compare the initial findings in the vestibular examination with the final diagnosis by otologists, neurologists and general practitioners. The complaints of 37.6% of the patients with these electronystagmographic (ENG) anomalies appeared to be of central origin. Abnormal saccades, an abnormal smooth pursuit, and an elevated gain in the torsion test were not independently diagnostic for central vestibular disease. The fixation suppression index appeared to be lower for subjects with peripheral vestibular disease. Otologists more often referred their patients to a neurologist if the fixation index was elevated.

Short form of the Dizziness Handicap Inventory: construction and validation through Rasch analysis

A new item response scale is presented, which measures the severity of self-reported balance deficits. The scale, DHIsf, is a short form of the Dizziness Handicap Inventory. The scale was constructed and validated by Rasch analysis. Rasch analysis was applied to rescore or remove any items misfitting, redundant, or off-target, until an optimal instrument was obtained. The 25-item, 3-level Dizziness Handicap Inventory was, thus, reduced to the 13-item, 2-level DHIsf. The retained items explore the domains of eye/head movements, full body activities, and mood alterations. Data were collected from 55 outpatients (63 +/- 13 yr; 43 females) attending otoneurological rehabilitation referral at a general hospital because of complaints of dizziness or imbalance. They were fully independent in ambulation and showed no evidence of major neurological or orthopedic diseases. Objective tests included brain computed tomography, sovraaorctic Doppler sonography, craniocorpography, static posturography, and nystagmography. The findings were categorized as pathologic, borderline, or normal. At least one examination was borderline or abnormal in 42 patients. The DHIsf was well targeted on this sample, with a mean score of 5.7/13 (standard deviation, 2.8; median, 5; range, 1-13). The Rasch statistics showed that the 13 items evenly fitted a hierarchy of difficulty within a homogeneous construct. A moderate but significant variance explanation of DHIsf measures was provided by a two-way analysis of variance model, with craniocorpography and nystagmography as independent categorical variables (r2 = 0.15; P = 0.018). When the clinical tests were individually taken into account, their outcome (dichotomized as abnormal v borderline or normal) could not be predicted by either of the DHIsf measures or raw scores (logistic regression). The DHIsf compares favorably with the original Dizziness Handicap Inventory, shows some consistency with the instrumental findings, and provides original information on the severity of imbalance syndromes, as it is seen from the patient's perspective.

Posturography does not test vestibulospinal function

The clinical usefulness of posturography is unknown, despite its costing more than +500 per test in some areas of the United States, including Boston. We cross-sectionally and prospectively studied blinded vestibulo-ocular and vestibulospinal tests from 29 stable patients with chronic vestibular hypofunction; 22 patients were affected bilaterally (BVH), and 7 were affected unilaterally (UVH). Vestibulo-ocular function was assessed by electronystagmographic caloric stimulation and sinusoidal vertical axis rotation gains at 0.05 Hz. Vestibulospinal function was assessed by moving-platform and visualsurround posturography sensory organization tests (SOTs), paced and free gait in a gait laboratory, and clinical tests of timed gait and standing. Posturography SOT moving-platform tests 4 through 6, designed to assess vestibular function, correlated significantly (r < or = 0.72, P > or = 0.01) with vestibulo-ocular tests in 5 of 6 comparisons among BVH patients. Posturography SOT results, however, correlated poorly with other vestibulospinal measures: correlations were statistically significant for only 7 of 18 comparisons with clinical balance and gait function (r < or = 0.69, P > or = 0.01) and with 2 of 12 comparisons for gait laboratory dynamic stability measures (r < or = 0.55, P > or = 0.01) among the BVH patients. When both the platform and visual surround moved (SOT 6), however, correlations were statistically significant with static standing clinical measures (r = 0.51 to 0.69, P < 0.01) and with whole-body maximum moment arm during paced gait (r = 0.55, P < 0.01). Posturography scores for the UVH patients did not significantly correlate with any vestibulo-ocular or other vestibulospinal measures. These data indicate that among patients with BVH posturography SOT scores relate at best modestly with accepted measure of vestibulo-ocular function, less well with clinical measures of balance control, and poorly with dynamic gait-performance measures. We conclude that posturography SOT does not assess vestibulospinal function.

Computerized dynamic platform posturography

Computerized dynamic platform posturography is defined in this technology assessment. The review discusses what computerized dynamic platform posturography measures, what the reliability and validity of the information are, and the uniqueness of the information provided. The clinical contribution and indications for testing are discussed. There are comments on future directions for research on computerized dynamic platform posturography and a summary and conclusion.

Potentially predictive and manipulable blood serum correlates of aging in the healthy human male: progressive decreases in bioavailable testosterone, dehydroepiandrosterone sulfate, and the ratio of insulin-like growth factor 1 to growth hormone

A cross-sectional survey was made in 56 exceptionally healthy males, ranging in age from 20 to 84 years. Measurements were made of selected steroidal components and peptidic hormones in blood serum, and cognitive and physical tests were performed. Of those blood serum variables that gave highly significant negative correlations with age (r > -0.6), bioavailable testosterone (BT), dehydroepiandrosterone sulfate (DHEAS), and the ratio of insulin-like growth factor 1 (IGF-1) to growth hormone (GH) showed a stepwise pattern of age-related changes most closely resembling those of the age steps themselves. Of these, BT correlated best with significantly age-correlated cognitive and physical measures. Because DHEAS correlated well with BT and considerably less well than BT with the cognitive and physical measures, it seems likely that BT and/or substances to which BT gives rise in tissues play a more direct role in whatever processes are rate-limiting in the functions measured and that DHEAS relates more indirectly to these functions. The high correlation of IGF-1/GH with age, its relatively low correlation with BT, and the patterns of correlations of IGF-1/GH and BT with significantly age-correlated cognitive and physical measures suggest that the GH-IGF-1 axis and BT play independent roles in affecting these functions. Serial determinations made after oral ingestion of pregnenolone and data from the literature suggest there is interdependence of steroid metabolic systems with those operational in control of interrelations in the GH-IGF-1 axis. Longitudinal concurrent measurements of serum levels of BT, DHEAS, and IGF-1/GH together with detailed studies of their correlations with age-correlated functional measures may be useful in detecting early age-related dysregulations and may be helpful in devising ameliorative approaches.