Effect of Rotating Auditory Scene on Postural Control in Normal Subjects, Patients With Bilateral Vestibulopathy, Unilateral, or Bilateral Cochlear Implants

Sound and postural control during stance tasks in abnormal subjective haptic vertical

BACKGROUND

Patients with vestibular impairment often suffer from postural instability. This could be compensated by other sensory systems such as the auditory system.

OBJECTIVE

The aim of this study was to investigate whether auditory input improves postural stability in patients with abnormal subjective haptic vertical (SHV).

METHODS

Participants (n = 13) with normal hearing and vision, but abnormal SHV participated. Participants performed standing on firm ground and foam support (eyes open/closed) and Tandem Romberg test (eyes closed) in quiet (reference), noise and with plugged ears. All tasks were conducted in a soundproofed and reverberant room. Postural stability was recorded close to the body's center of gravity. Reference conditions were compared with a control group.

RESULTS

In only two tasks sway increased significantly when noise was presented during challenging tasks in the soundproofed room. Sway of the reference conditions did not differ significantly between control and study group.

CONCLUSIONS

This study shows no influence of applied auditory stimulation on posture in participants with abnormal SHV in a reverberant room, but an adverse effect on balance during difficult tasks in the soundproofed room. Noise possibly masked auditory information that was helpful in improving posture in the quiet condition. Futhermore, noise might have distracted participants from maintaining balance.

Weighting of visual and auditory inputs in dancers with and without previous ankle injury

Elite dance requires highly controlled balance performance in dynamic visual and auditory environments characterized by the use of stage lighting and music. Perturbing visual input is known to influence balance in dancers, but the effects of sounds have not been clearly established. Ankle inversion injuries are common in dancers and may also play a role in dancers' ability to respond to sensory perturbations. The aims of this study were to identify changes in static balance in response to visual or auditory perturbation in elite collegiate dancers with and without a history of ankle injury, and to describe coupling of measurements obtained from the waist and head during balance. Thirty-seven dancers: 22 controls and 15 with a history of ankle sprain, performed single-leg balance under static and dynamic visual and auditory conditions. Dancers demonstrated increased waist sway when viewing a dynamic visual scene and when presented with moving sounds and increased head sway with dynamic visuals. These results did not vary by history of ankle sprain. While dancers appear to dampen the impact of waist sway on head motion during single leg stance, even highly trained dancers may experience challenges controlling balance under perturbing visual and auditory conditions like those present during stage performance.

Interaction of Hearing and Balance

There is increasingly assumed that, in addition to visual, vestibular and somatosensory afferents, hearing also plays a role in the regulation of balance. It seems that, especially in old age, progressive hearing loss is associated with a decrease in postural control. Several studies investigated this relationship in normal-hearing people, in patients with conventional hearing aids and with implantable hearing systems, as well as in patients with vestibular disorders. Despite the inhomogeneous study situation and lack of evidence, hearing seems to interact with the balance regulation system with potentially stabilizing effect. Furthermore, insights into audiovestibular interaction mechanisms could be achieved, which could possibly be integrated into therapeutic concepts of patients with vestibular disorders. However, further prospective controlled studies are necessary to bring this issue to an evidence-based level.

Influence of Hearing Rehabilitation With Active Middle Ear and Bone Conduction Implants on Postural Control

Background

As audition also seems to contribute to balance control, additionally to visual, proprioceptive, and vestibular information, we hypothesize that hearing rehabilitation with active middle ear and bone conduction implants can influence postural control.

Methods

In a prospective explorative study, the impact of hearing rehabilitation with active middle ear [Vibrant Soundbrige (VSB), MED-EL, Innsbruck, Austria] and bone conduction implants [Bonebridge (BB), MED-EL, Innsbruck, Austria] on postural control in adults was examined in three experiments. Vestibulospinal control was measured by cranio-corpography (CCG), trunk sway velocity (°/s) by the Standard Balance Deficit Test (SBDT), and postural stability with a force plate system, each time in best aided (BA) and unaided (UA) condition with frontal-noise presentation (Fastl noise, 65 dB SPL), followed by subjective evaluation, respectively.

Results

In 26 subjects [age 55.0 ± 12.8 years; unilateral VSB/BB: n = 15; bilateral VSB/BB: n = 3, bimodal (VSB/BB + hearing aid): n = 8], CCG-analysis showed no difference between BA and UA conditions for the means of distance, angle of displacement, and angle of rotation, respectively. Trunk sway measurements revealed a relevant increase of sway in standing on foam (p = 0.01, r = 0.51) and a relevant sway reduction in walking (p = 0.026, r = 0.44, roll plane) in BA condition. Selective postural subsystem analysis revealed a relevant increase of the vestibular component in BA condition (p = 0.017, r = 0.47). As measured with the Interactive Balance System (IBS), 42% of the subjects improved stability (ST) in BA condition, 31% showed no difference, and 27% deteriorated, while no difference was seen in comparison of means. Subjectively, 4–7% of participants felt that noise improved their balance, 73–85% felt no difference, and 7–23% reported deterioration by noise. Furthermore, 46–50% reported a better task performance in BA condition; 35–46% felt no difference and 4–15% found the UA situation more helpful.

Conclusions

Subjectively, approximately half of the participants reported a benefit in task performance in BA condition. Objectively, this could only be shown in one mobile SBDT-task. Subsystem analysis of trunk sway provided insights in multisensory reweighting mechanisms.

Auditory Input and Postural Control in Adults: A Narrative Review

Importance

An increase in the number of mechanistic studies targeting the association between sound and balance has been observed in recent years, but their results appear equivocal.

Observations

A search of PubMed and the Cochrane Database of Systematic Reviews for English-language studies on auditory input and postural control published from database inception through October 31, 2019, yielded 28 articles for review. These articles included 18 (64%) studies of healthy adults, 1 (4%) of participants with Alzheimer disease, 2 (7%) of participants with congenital blindness, 3 (11%) of participants with vestibular loss, and 4 (14%) of participants with diverse levels of hearing loss. Studies varied by the type of audio stimuli (natural vs generated sounds), apparatus (speakers vs headphones), and movement of sounds (eg, stationary, rotational). Most balance measurements involved standing on the floor or foam with eyes open or closed during which sway amount or velocity was quantified. Stationary broadband sounds, including white or environmental noise, may improve balance, but the results regarding stationary pure tone were inconclusive. The implication of moving sounds varied by apparatus (typically destabilizing when headphones were used) and sensory loss (more destabilizing with vestibular or hearing loss but perhaps less with a unilateral cochlear implant).

Conclusions and Relevance

Findings from this review suggest that stationary broadband noise can serve as an auditory anchor for balance primarily when projected via speakers and when the balance task is challenging. More research is needed that includes individuals with sensory loss and that tests paradigms using dynamic, ecologically valid sounds; clinicians should also consider auditory cues and the presence of hearing loss in balance and fall-risk assessments.

Can hearing amplification improve presbyvestibulopathy and/or the risk-to-fall ?

Purpose

The decline of sensory systems during aging has been widely investigated and several papers have correlated the visual, hearing and vestibular systems and the consequences of their functional degeneration. Hearing loss and presbyvestibulopathy have been found to be positively correlated as is with the risk-to-fall.

Material and methods

The present study was therefore designed as systematic review (due to PRISMA criteria) which should correlate hearing amplification by hearing aids and/or cochlear implants with balance outcome. However, the literature review (Cochrane, PubMed) revealed ten paper (prospective, controlled trials and acute trials) with heterogenous patient popiulations and non-uniform outcome measures (i.e., gait analysis, questionnaires, postural stabilometry) so that no quantitative, statistical analysis could be performed.

Results

The qualitative analysis oft he identified studies showed that hearing amplification in the elderly improves spatio-temporal orientation (particularly with cochlear implants) and that the process of utilizing auditory information for balance control takes some time (i.e., the neuroplasticity-based, learning processes), usually some months in cochlear implantees.

Discussion

Hearing and balance function degenerate independently from each other and large interindividual differences require a separate neurotological examination of each patient. However, hearing amplification is most helpful to improve postural stability, particularly in the elderly. Future research should focus on controlled, prospective clinical trials where a standardized test battery covering the audiological and neurotological profile of each elderly patient pre/post prescription of hearing aids and/or cochlear implantation should be followed up (for at least 1 year) so that also the balance improvements and the risk-to-fall can be reliably assessed (e.g., by mobile posturography and standardized questionnaires, e.g., the DHI).

A Systematic Review on Balance Performance in Patients With Bilateral Vestibulopathy

OBJECTIVE

Patients with bilateral vestibulopathy (BVP) have severe balance deficits, but it is unclear which balance measures are best suited to quantify their deficits and approximate the diversity of their self-reports. The purpose of this study was to explore measures of balance control for quantifying the performance of patients with BVP related to different balance domains, allowing targeted assessment of response to intervention.

METHODS

MEDLINE, Web of Science, and Embase were systematically searched on October 9, 2019. The Scottish Intercollegiate Guidelines Network checklist for case-control studies was applied to assess each individual study's risk of bias. Standardized mean differences (SMD) were calculated based on the extracted numeric data and reported according to the type of sensory perturbation in the balance tasks.

RESULTS

Twelve studies (1.3%) met the eligibility criteria and were analyzed, including data of 176 patients with BVP, 196 patients with unilateral vestibulopathy, and 205 healthy controls between 18 and 92 years old. In general, patients with BVP were either unable to maintain (or had reduced) balance during tasks with multisensory perturbations compared with healthy controls (range of mean SMD = 1.52-6.92) and patients with unilateral vestibulopathy (range of absolute mean SMD = 0.86-1.66).

CONCLUSIONS

During clinical assessment to quantify balance control in patients with BVP, tasks involving multisensory perturbations should be implemented in the test protocol.

IMPACT

As patients with BVP show difficulties with movement strategies, control of dynamics, orientation in space, and cognitive processing, clinicians should implement these aspects of balance control in their assessment protocol to fully comprehend the balance deficits in these patients.

Frequency analyses of posturography using logarithmic translation

Background: Power-spectral analysis of the centre of pressure (CoP) frequencies of posturography provides exponentially approximated distributions, whereas logarithmic translation enables linear approximation.Objectives: Frequency analyses were adopted for posturography of healthy subjects and patients with spinocerebellar degeneration (SCD) using logarithmic translation to determine its clinical usefulness for managing the elderly and patients with disequilibrium.Material and methods: We included 172 healthy subjects and 47 SCD patients. Posturography was performed with the eyes fixated and closed, with and without foam rubber. The power-spectral data of the CoP were obtained with the maximum entropy method. Power-spectral data were logarithmically translated for quantitative evaluation.Results: For teenagers, high-frequency fluctuations were dominant and attributable to proprioceptive compensation due to immature postural control. In elderly populations, the increased frequency in the lateral direction was characterised by three peaks indicating postural disturbances attributed to three sensory inputs. The disappearance of one peak in the anteroposterior fluctuation indicates a decrease in vestibular contribution. The foam rubber and the closed-eye condition enhanced fluctuations in two peaks. There were differences in power-spectral distributions of two peaks between the healthy subjects and SCD patients.Conclusions: Logarithmic power-spectral data distribution could provide an age- and disease-specific novel and visually-comprehensible parameter.