Hearing loss versus vestibular loss as contributors to cognitive dysfunction

Associations Between Vestibular Perception and Cognitive Performance in Healthy Adults

OBJECTIVES

A growing body of evidence has linked vestibular function to the higher-order cognitive ability in aging individuals. Past evidence has suggested unique links between vestibular function and cognition on the basis of end-organ involvement (i.e., otoliths versus canals). However, past studies have only assessed vestibular reflexes despite the diversity of vestibular pathways. Thus, this exploratory study aimed to assess associations between vestibular perception and cognition in aging adults to determine potential relationships.

DESIGN

Fifty adults (21 to 84 years; mean = 52.9, SD = 19.8) were included in this cross-sectional study. All participants completed a vestibular perceptual threshold test battery designed to target perception predominantly mediated by each end-organ pair and intra-vestibular integration: 1 Hz y -translation (utricle), 1 Hz z -translation (saccule), 2 Hz yaw rotation (horizontal canals), 2 Hz right anterior, left posterior (RALP), and left anterior, right posterior (LARP) tilts (vertical canals), and 0.5 Hz roll tilt (canal-otolith integration). Participants also completed standard assessments of cognition and path integration: Digit Symbol Substitution Test (DSST), Trail Making Test (TMT), and the Gait Disorientation Test (GDT). Associations were assessed using Spearman rank correlation, and multivariable regression analyses.

RESULTS

For correlation analyses, DSST correlated to RALP/LARP tilt, roll tilt, and z -translation. TMT-A only correlated to z -translation, and TMT-B correlated to roll tilt and z -translation after correcting for multiple comparisons. GDT correlated to RALP/LARP tilt and y -translation. In age-adjusted regression analyses, DSST and TMT-B were associated with z -translation thresholds and GDT was associated with y -translation thresholds.

CONCLUSIONS

In this cross-sectional study, we identified associations between vestibular perceptual thresholds with otolith contributions and standard measures of cognition. These results are in line with past results suggesting unique associations between otolith function and cognitive performance.

Concurrent Cognitive Task Alters Postural Control Performance of Young Adults With Unilateral Cochlear Implants

PURPOSE

The aim of this study was to investigate the balance performances of young adults with unilateral cochlear implants (CIs) in a dual-task condition.

METHOD

Fifteen young adults with unilateral CIs and 15 healthy individuals were included in the study. The balance task was applied using the Sensory Organization Test via Computerized Dynamic Posturography. The Backward Digit Recall task was applied as an additional concurrent cognitive task. In the balance task, participants completed four different conditions, which gradually became more difficult: Condition 1: fixed platform, eyes open; Condition 3: fixed platform, eyes open and visual environment sway; Condition 4: platform sway, eyes open; Condition 6: platform sway, eyes open and visual environment sway. To evaluate the dual-task condition performance, participants were given cognitive and motor tasks simultaneously.

RESULTS

Visual (p = .016), vestibular (p < .001), and composite balance scores (p < .001) of CI users were statistically significantly lower than the control group. Condition 3 (p = .003), Condition 4 (p = .007), and Condition 6 (p < .001) balance scores of CI users in the single-task condition were statistically significantly lower than controls. Condition 6 (p < .001) balance scores of CI users in the dual-task condition were statistically significantly lower than the control group. Condition 1 score (p = .002) of the CI users in the dual-task condition showed a statistically significant decrease compared to the balance score in the single-task condition, while the Condition 6 score (p = .011) in the dual-task condition was statistically significantly higher than the balance score in the single-task condition.

CONCLUSIONS

The balance performance of individuals with CIs in the dual-task condition was worse than typical healthy individuals. It can be suggested that dual-task performances should be included in the vestibular rehabilitation process in CI users in the implantation process in terms of balance abilities in multitasking conditions and risk of falling.

Abnormalities of resting-state EEG microstates in older adults with cognitive frailty

This study aims to analyze the characteristics of EEG microstates across different cognitive frailty (CF) subtypes, providing insights for the prevention and early diagnosis of CF. This study included 60 eligible older adults. Their resting-state EEG microstates were analyzed using agglomerative adaptive hierarchical clustering. Microstate temporal parameters were extracted through global field power peak-based backfitting. Spearman's partial correlation analysis and linear mixed-effects models were employed to investigate the relationship between microstate temporal parameters and CF. Statistical differences were observed in transition probabilities (TPs) from microstate B to A between healthy controls (HCs) and reversible cognitive frailty (RCF) group (t = -2.076, P = 0.042). Potentially reversible cognitive frailty (PRCF) and RCF group also exhibited statistical differences in the TPs from microstate B to A (t = 3.122, P = 0.003). In the RCF group, the occurrence of microstates A and B differed significantly from microstate C (tAC = 3.455, PAC = 0.002; tBC = 3.108, PBC = 0.004). In the PRCF group, the occurrence of microstates A, B, and C differed significantly from microstate D (tAD = -3.688, PAD = 0.001; tBD = -3.334, PBD = 0.002; tCD = -4.188, PCD < 0.001). The neural networks and processing modes engaged by microstate D during executive memory tasks differ between RCF and PRCF. A decreased occurrence of microstate C and higher TPs of microstates A and B may serve as early warning signals for RCF. Conversely, an increased occurrence of microstate D and decreased TPs of microstates C and D indicate the onset of PRCF.

Postural imbalance without visual input is associated with specific neuropsychological deficits in older adults - results from the LIFE-adult study

Introduction

Modifiable risk factors play an important role in preventing dementia and reducing its progression. Regular physical activity already in midlife, which relies on intact multisensory balance control, can help to decrease the risk of dementia. However, our understanding of the relationship between postural balance and cognitive functions remains limited. The objective of our study was to investigate the association of postural balance during different sensory conditions with specific cognitive domains in older adults.

Methods

Participants were from the population-based prospective "Leipzig Research Center for Civilization Diseases" (LIFE-Adult) cohort in Leipzig, Germany. Executive, memory and processing speed functions were tested by the Consortium to Establish a Registry for Alzheimer's disease (CERAD) plus battery. Assessment of visuospatial abilities was based on the short form of the Judgment of Line Orientation Test (JLO). Postural sway was recorded on a force plate with eyes open and closed. Romberg's ratios were calculated for sway path and sway area as a proxy for balance without visual control and tested in generalized linear regression models with the summary scores of executive function, memory, processing speed and visuospatial function as dependent variables. All models were adjusted for sex, age, ApoE status, socioeconomic status, anamnestic stroke, and diabetes.

Results

In total, we analyzed 460 participants with a mean age of 68.6 years, range 60 to 80, 47.6% female. A higher Romberg's ratio for sway area was a significant indicator for impaired visuospatial abilities as measured by the dichotomized JLO (Odds Ratio = 1.42, 95% confidence interval 1.07 to 1.88). Romberg's ratios were not significantly associated with executive functions, procedural speed or memory functions.

Discussion

It may be worthwhile to examine in the future whether inclusion of balance testing enhances the value of screening programs for cognitive impairment. Inversely, it may be appropriate to apply routine cognitive tests when balance problems are detected in older patients.

Sensorineural Hearing Loss Negatively Impacts Cognition in Older Subjects with Normal Lateral Semi-Circular Canal Function

INTRODUCTION

Worldwide around 400 million people suffer from hearing loss. There is increasing evidence that hearing loss is a modifiable risk factor for cognitive decline. However, several risk factors for cognition are common in hearing-impaired individuals, including vestibular dysfunction, anxiety, and depression. This study aimed to explore the effect of hearing loss on cognitive functioning in older adults, considering the effects of vestibular function, anxiety, and depression on cognitive performance.

METHOD

A cross-sectional study was performed on 42 subjects with moderate-to-severe sensorineural hearing loss (SNHL) and 42 matched normal-hearing controls. Matching was based on the following factors; sex, age, education level, level of anxiety and depression, and vestibular function. The test battery consisted of a cognitive assessment (Repeatable Battery for the Assessment of Neuropsychological Status adjusted for the Hearing Impaired [RBANS-H]), hearing assessment (Pure Tone Average and speech-in-noise testing), and vestibular assessment (video Head Impulse Test [vHIT]). Depression and anxiety were evaluated using the Hospital Anxiety and Depression Scale (HADS) and Beck Depression Inventory (BDI) questionnaires.

RESULTS

A significantly lower total cognitive (RBANS-H) score was observed in the group with SNHL compared to controls (100.93 [12.94] vs. 108.88 [10.47], p = 0.003). The difference among both groups was most pronounced in the subdomains Visuospatial/Constructional (92.90 [16.32] vs. 103.12 [12.83], p = 0.002) and Attention (96.62 [12.52] vs. 104.02 [11.81], p = 0.007). The other subdomains Immediate Memory, Language, and Delayed Memory did not differ significantly between the groups with SNHL and the normal-hearing controls.

CONCLUSION

The results of this study indicate that hearing loss negatively affects cognitive functioning, even in older adults with normal vestibular function.

Animal studies linking the vestibular system and memory: Aotearoa/New Zealand's contribution

Animal studies of the mammalian vestibular system began at the University of Otago in 1987. From approximately 2000, these studies focused on the effects of vestibular lesions and stimulation, on spatial memory and the hippocampus. Our research has shown that, as well as the deficits in the vestibulo-ocular and vestibulo-spinal reflexes that occur following vestibular dysfunction, vestibular loss may also cause cognitive disorders, especially spatial memory deficits, some of which are related to the contribution of ascending vestibular pathways to the function of the limbic system and neocortex in regulating spatial orientation. In addition to behavioural demonstrations of spatial memory deficits, we have demonstrated that vestibular loss is associated with a variety of dysfunctional changes in the hippocampus, which may be responsible for the spatial memory deficits. These memory deficits are unlikely to be due to hearing loss, problems with motor control, oscillopsia or anxiety and depression. These animal studies have raised awareness of cognitive deficits associated with vestibular disorders and contributed to their recognition and treatment.

Assessment of Otolith Function with Subjective Visual Vertical Test in Sensorineural Hearing Loss: An Analytical Cross - Sectional Study

The inner ear is responsible for balance and auditory function. Sensorineural hearing loss (SNHL) affects auditory function across various age groups. Vestibular apparatus, particularly the otolith organ can also be affected in cases of SNHL because of the close proximity of the otolith organs with the cochlea inside the bony labyrinth. The otolith organs can be assessed with Subjective Visual vertical test (SVV), which is a simple, rapid, non-invasive test with high sensitivity and specificity. Present study was conducted with the objective to compare the SVV parameters between normal and SNHL patients and to correlate between the degree of tilt in SVV with severity of SNHL. A convenient sample size of 60 was taken of which 30 were control and 30 were SNHL patients. PTA and SVV were performed on both groups and results were analysed in IBM SPSS version 26. Age stratified analysis between the control group and SNHL group for the age group 20-40 years and for > 40 years revealed a significant statistical difference in the average static SVV (P = 0.019 and P = 0.009 for age group 20-40 years and > 40 years respectively) and dynamic anti clockwise SVV (P = 0.024 and P = 0.031 for age group 20-40 years, and > 40 years respectively) between the control group and the SNHL group. Correlational analysis also shows a moderate correlation between the bone conduction threshold and the various SVV parameters. Statistical difference of SVV parameters between the two groups suggests a possible early involvement of the otolith organ in SNHL. As such the utility of SVV as an early marker for otolith dysfunction needs to be further explored. It may be worthwhile to follow up the patients of SNHL longitudinally and assess the otolith function with SVV at periodic intervals to identify any progression.

Association Between Hearing Loss, Asymmetric Hearing, and Postural Instability

OBJECTIVES

Recent studies have suggested that older adults with hearing loss (HL) are at a greater risk of postural instability than those with normal hearing. However, little is known regarding this association in middle-aged individuals. The relationships between HL laterality, asymmetric hearing, and posture control are similarly unclear. The purpose of this study was to investigate the effects of hearing status on postural control and to explore the dose-response relationship between the hearing threshold and postural instability risk in middle-aged adults.

DESIGN

This cross-sectional study included 1308 participants aged 40 to 69 years with complete audiometric and standing balance function data from the 2001-2004 National Health and Nutrition Examination Survey. Speech-frequency HL was defined as a pure-tone average at 0.5, 1, 2, and 4 kHz of >25 dB in the better-hearing ear; high-frequency HL was defined as a pure-tone average at 3, 4, and 6 kHz of >25 dB. Asymmetric hearing was defined as a difference in the pure-tone average >15 dB between ears. Postural instability was defined as participants ending the modified Romberg test in condition 4.

RESULTS

After adjustment for sociodemographic variables, lifestyle, and comorbidities, speech-frequency HL, except for unilateral HL, was associated with increased postural instability (mild HL: odds ratio [OR], 2.33; 95% confidence interval [CI], 1.25-4.35; moderate-to-severe HL: OR, 3.59; 95% CI, 1.61-8.03). Compared with individuals with normal bilateral hearing, participants with bilateral HL also showed a higher risk of postural instability (OR, 2.88; 95% CI, 1.61-5.14). The OR for postural instability among participants with asymmetric hearing compared with those with symmetric hearing was 2.75 (95% CI, 1.37-5.52). Furthermore, each 10 dB increase in the speech-frequency hearing threshold was associated with a 44% higher risk of postural instability.

CONCLUSIONS

Hearing loss is associated with poorer postural control. Individuals with asymmetric hearing have a higher postural instability risk compared with those with symmetric hearing. Further studies are needed to confirm these findings and the causality. Moreover, future studies are warranted to assess whether hearing aids are beneficial for the restoration of impaired balance functions.

Anti-saccade as a tool to evaluate cognitive impairment in vestibular migraine

Background

Vestibular migraine (VM), an intricate subtype of migraine, amalgamates the dual attributes of migraine and vestibular disorders. In clinical settings, individuals with VM frequently articulate concerns regarding the manifestation of subjective cognitive impairment. This cognitive dysfunction is intricately linked with diminished mobility, heightened susceptibility to falls, and increased absenteeism in afflicted patients. Consequently, comprehending the features of cognitive impairment in VM patients holds potential clinical significance. The pursuit of rapid and objective methods for detection and assessment is foundational and prerequisite for efficacious cognitive management of VM patients.

Methods

The study encompassed 50 patients diagnosed with vestibular migraine and recruited 50 age-sex matched healthy controls. All participants underwent anti-saccade tasks, and cognitive evaluation was performed using the MMSE and MoCA to assess overall cognitive function. Additionally, RBANS scales were employed to measure specific cognitive domains.

Results

The VM patients and normal controls demonstrated statistical parity in terms of age, gender, education, weight, and BMI, with no significant differences observed. Analysis of cognitive scores divulged a marked increase in the incidence of Mild Cognitive Impairment (MCI) in VM patients compared to Healthy Controls (HCs). Both MMSE and MoCA scores were notably lower in VM patients compared to their healthy counterparts. The RBANS cognitive test indicated significant impairment in immediate memory, visuospatial construction, language, attention, and delayed memory among VM patients. Notably, the Trail Making Test and Stroop Color-Word Test revealed compromised processing speed and executive function cognitive domains. The anti-saccadic task highlighted significantly elevated anti-saccadic latency and frequency of direction errors in vestibular migraine patients. Symptom severity, illness duration, and episode frequency in VM patients positively correlated with counter-scanning errors and negatively correlated with cognitive performance across diverse cognitive domains.

Conclusion

VM patients exhibit cognitive decline across multiple cognitive domains during the interictal period. This cognitive impairment may not be fully reversible, underscoring its potential clinical significance for cognitive management in VM patients. The sensitivity of anti-saccade tasks to the cognitive status of VM patients positions them as promising objective indicators for diagnosis, intervention, and evaluation of cognitive impairment effects in VM in future applications.

Executive functions in patients with bilateral and unilateral peripheral vestibular dysfunction

Previous research suggests that patients with peripheral vestibular dysfunction (PVD) suffer from nonspatial cognitive problems, including executive impairments. However, previous studies that assessed executive functions are conflicting, limited to single executive components, and assessments are confounded by other cognitive functions. We compared performance in a comprehensive executive test battery in a large sample of 83 patients with several conditions of PVD (34 bilateral, 29 chronic unilateral, 20 acute unilateral) to healthy controls who were pairwise matched to patients regarding age, sex, and education. We assessed basic and complex executive functions with validated neuropsychological tests. Patients with bilateral PVD performed worse than controls in verbal initiation and working memory span, while other executive functions were preserved. Patients with chronic unilateral PVD had equal executive performance as controls. Patients with acute unilateral PVD performed worse than controls in the exact same tests as patients with bilateral PVD (verbal initiation, working memory span); however, this effect in patients with acute PVD diminished after correcting for multiple comparisons. Hearing loss and affective disorders did not influence our results. Vestibular related variables (disease duration, symptoms, dizziness handicap, deafferentation degree, and compensation) did not predict verbal initiation or working memory span in patients with bilateral PVD. The results suggest that bilateral PVD not only manifests in difficulties when solving spatial tasks but leads to more general neurocognitive deficits. This understanding is important for multidisciplinary workgroups (e.g., neurotologists, neurologists, audiologists) that are involved in diagnosing and treating patients with PVD. We recommend screening patients with PVD for executive impairments and if indicated providing them with cognitive training or psychoeducational support.

Vestibular dysfunction and its association with cognitive impairment and dementia

The vestibular system plays an important role in maintaining balance and posture. It also contributes to vertical perception, body awareness and spatial navigation. In addition to its sensory function, the vestibular system has direct connections to key areas responsible for higher cognitive functions, such as the prefrontal cortex, insula and hippocampus. Several studies have reported that vestibular dysfunction, in particular bilateral vestibulopathy, is associated with an increased risk of cognitive impairment and the development of dementias such as Alzheimer's disease. However, it is still controversial whether there is a causal relationship between vestibular damage and cognitive dysfunction. In this mini-review, we will explore the relationship between the vestibular system, cognitive dysfunction and dementia, hypotheses about the hypothesis and causes that may explain this phenomenon and also some potential confounders that may also lead to cognitive impairment. We will also review multimodal neuroimaging approaches that have investigated structural and functional effects on the cortico-vestibular network and finally, describe some approaches to the management of patients with vestibular damage who have shown some cognitive impairment.

Does Hearing Impairment Impact Spatial Orientation, Navigation, and Rotation Abilities?

OBJECTIVES

Spatial cognition is a perceptual-motor function that pertains to the comprehension and processing of two-dimensional and three-dimensional space. The impairment of any sensory system can have adverse effects on cognitive functioning. The objective of this study is to examine spatial cognition in adults with hearing impairments.

METHODS

There were a total of 61 individuals in this study: thirty-six with hearing loss and 25 with normal hearing. The Spatial Orientation Test (SOT), the Mental Rotation test (MR), and the Money's Road Map Test (RMT) were administered to assess participants' spatial learning-orientation, mental imagery-rotation, and spatial navigation abilities. A high number of errors in RMT, high angle difference in SOT and a low score in MR suggest poor spatial abilities.

RESULTS

Participants with hearing loss had a greater number of RMT errors and SOT angle difference, but lower MR scores than those with normal hearing (P < .001). Hearing impairment negatively impacted all 3 spatial cognitive assessments. Hearing loss was associated with a 6.9 increase in the number of RMT errors (95% Confidence Interval (CI): 4.8, 9), a 23.6 increase in the SOT angle difference (95% CI: 16, 31.2), and an 8.5 decrease in the MR score (95% CI: -10.8, -6.2).

CONCLUSIONS

The study found that individuals with hearing loss exhibited lower performance in various cognitive tasks related to spatial orientation, navigation, spatial learning, mental imagery, and rotation abilities when compared to an age and sex matched control group. In future study, it is imperative to place greater emphasis on hearing loss as a potential detrimental factor in the prediction of spatial cognition impairment.

Impact and experiences of vestibular disorders and psychological distress: Qualitative findings from patients, family members and healthcare professionals

INTRODUCTION

People with vestibular disorders frequently experience reduced quality of life and challenges with activities of daily living. Anxiety, depression and cognitive problems often co-present with vestibular disorders and can aggravate symptoms and prolong clinical recovery. We aimed to gain in-depth insights into the impact of vestibular disorders and the contribution of psychological factors by exploring multistakeholder perspectives.

METHODS

Semistructured interviews were conducted between October 2021 and March 2022 with 47 participants in the United Kingdom including: 20 patients (age M = 50.45 ± 13.75; 15 females), nine family members (age M = 61.0 ± 14.10; four females), and 18 healthcare professionals. Data were analysed using framework analysis.

RESULTS

Vestibular disorders impact diverse aspects of patients' lives including work, household chores, socialising, and relationships with family and friends. Being unable to engage in valued activities or fulfil social roles contributes to feelings of grief and frustration, affecting identity, confidence, and autonomy. Anxiety and low mood contribute to negative thought processes, avoidance, and social withdrawal, which can impede clinical recovery through reduced activity levels, and end engagement with treatment. Coping strategies were thought to help empower patients to self-manage their symptoms and regain a sense of control, but these require oversight from healthcare providers.

CONCLUSIONS

Daily activity limitations, social participation restrictions, and psychological distress can interact to impact quality of life, sense of self, and clinical recovery amongst people with vestibular disorders. Information and resources could aid societal awareness of the impact of vestibular disorders and help patients and families feel understood. An individualised and comprehensive approach that concurrently addresses mental, physical, social, and occupational needs is likely to be beneficial.

PATIENT OR PUBLIC CONTRIBUTION

Two group meetings were held at the beginning and end of the study with a patient and public involvement network formed of people with vestibular disorders and family members. These individuals commented on the study aims, interview schedule, participant recruitment practices, and interpretation of the themes identified. Two core patient members were involved at all stages of the research. These individuals contributed to the formulation of the interview schedule, development and application of the coding scheme, development and interpretation of themes, and preparation of the final manuscript.

Aging of the vestibular system and its relationship to dementia

PURPOSE OF REVIEW

Since October 2022, substantial new information has been published on age-related effects on the vestibular system. Since much of this evidence relates to the risk of dementia, the purpose of this review will be to provide an overview of this new information and critically evaluate it.

RECENT FINDINGS

This review will address studies published since October 2022 regarding age-related effects on the vestibular system and their relationship to cognition and dementia. There has been a particular increase in the last year in the number of studies relating aging of the vestibular system to Alzheimer's disease (AD), further supporting the view that vestibular dysfunction is associated with an increased risk of dementia.

SUMMARY

The conclusion of these recent studies is that, consistent with previous studies, vestibular function declines with age, and that this age-related decline is associated with cognitive impairment and an increased risk of dementia. Efforts are being made to consider these implications for cognition in the treatment of vestibular disorders.

Central vestibular networking for sensorimotor control, cognition, and emotion

PURPOSE OF REVIEW

The aim of this study was to illuminate the extent of the bilateral central vestibular network from brainstem and cerebellum to subcortical and cortical areas and its interrelation to higher cortical functions such as spatial cognition and anxiety.

RECENT FINDINGS

The conventional view that the main function of the vestibular system is the perception of self-motion and body orientation in space and the sensorimotor control of gaze and posture had to be developed further by a hierarchical organisation with bottom-up and top-down interconnections. Even the vestibulo-ocular and vestibulo-spinal reflexes are modified by perceptual cortical processes, assigned to higher vestibulo-cortical functions. A first comparative fMRI meta-analysis of vestibular stimulation and fear-conditioning studies in healthy participants disclosed widely distributed clusters of concordance, including the prefrontal cortex, anterior insula, temporal and inferior parietal lobe, thalamus, brainstem and cerebellum. In contrast, the cortical vestibular core region around the posterior insula was activated during vestibular stimulation but deactivated during fear conditioning. In recent years, there has been increasing evidence from studies in animals and humans that the central vestibular system has numerous connections related to spatial sensorimotor performance, memory, and emotion. The clinical implication of the complex interaction within various networks makes it difficult to assign some higher multisensory disorders to one particular modality, for example in spatial hemineglect or room-tilt illusion.

SUMMARY

Our understanding of higher cortical vestibular functions is still in its infancy. Different brain imaging techniques in animals and humans are one of the most promising methodological approaches for further structural and functional decoding of the vestibular and other intimately interconnected networks. The multisensory networking including cognition and emotion determines human behaviour in space.

Cognition in vestibular disorders: state of the field, challenges, and priorities for the future

Vestibular disorders are prevalent and debilitating conditions of the inner ear and brain which affect balance, coordination, and the integration of multisensory inputs. A growing body of research has linked vestibular disorders to cognitive problems, most notably attention, visuospatial perception, spatial memory, and executive function. However, the mechanistic bases of these cognitive sequelae remain poorly defined, and there is a gap between our theoretical understanding of vestibular cognitive dysfunction, and how best to identify and manage this within clinical practice. This article takes stock of these shortcomings and provides recommendations and priorities for healthcare professionals who assess and treat vestibular disorders, and for researchers developing cognitive models and rehabilitation interventions. We highlight the importance of multidisciplinary collaboration for developing and evaluating clinically relevant theoretical models of vestibular cognition, to advance research and treatment.

Quantitative analysis of balance function characteristics in older patients with mild to moderate cognitive impairment

BACKGROUND

Cognitive decline in older adults may affect balance function, but the relationship between the two is not fully understood, especially in the early stages of cognitive impairment. Mild to moderate cognitive impairment can be assessed with the Montreal Cognitive Assessment (MOCA).

AIM

This study quantitatively analyzed balance function in older adults with mild to moderate cognitive impairment using computerized dynamic posturography (CDP) testing.

METHODS

248 older patients were divided into a cognitive impaired group (MOCA <26, n = 126) and a normal group (MOCA ≥26, n = 122) based on the Montreal Cognitive Assessment (MOCA) Beijing Version. Patients underwent CDP testing, which included the sensory organization test (SOT) and the limits of stability test (LOS).

RESULTS

The cognitive impaired group had significantly lower SOT composite and visual scores, as well as reaction time (RT), movement velocity (MVL), endpoint excursion (EPE), maximum excursion (MXE), and directional control (DCL) of the LOS test. Binary logistic regression analysis revealed that RT and MXE were independent factors significantly associated with MOCA, even after adjustment for age and sex.

CONCLUSIONS

Older patients with mild to moderate cognitive impairment may have reduced sensory integration and balance stability limits, mainly manifested as prolonged motor reaction time and shortened maximum movement distance.

Relationship between vestibular loss and the risk of dementia using the 2002-2019 national insurance service survey in South Korea

This retrospective cross-sectional study assessed older adults aged between 40 and 80 years, registered in the Korean National Health Insurance Service database from 2002 to 2019 to investigate the association between vestibular loss and the risk of dementia. The population was divided into three groups (general, vestibular loss, and hearing loss). The hazard ratios (HRs) of dementia in the vestibular and hearing loss groups were calculated using national population data. In total, 2,347,610 individuals were identified (general: 2,145,609, vestibular loss: 60,525, hearing loss: 141,476). Mean ages were 53.29 years, 58.26 years, and 58.52 years, respectively. Dementia occurred in 127,081 (IR = 4.91 per 1000 person-years), 7705 (IR = 10.79 per 1000 person-years), and 16,116 (IR = 9.63 per 1000 person-years) patients. The vestibular and hearing loss groups had hazard ratios for dementia of 1.084 (95% CI, 1.059-1.110) and 1.074 (95% CI, 1.056-1.092), respectively, compared with the general group. The results of the current study suggest that vestibular loss increases the risk of developing dementia. Therefore, similar to hearing loss, vestibular loss should be considered a risk factor for dementia, and treatments such as adequate vestibular rehabilitation may reduce this risk.

A cross-sectional study on the neurocognitive outcomes in vestibular impaired school-aged children: are they at higher risk for cognitive deficits?

This study aimed to assess if children with a vestibular impairment (VI) are more prone to have neurocognitive deficits compared to typically developing (TD) peers, taking into account important confounding factors with hearing loss being the most important. The neurocognitive performance of fifteen VI children (6-13 years old) was compared to that of an age-, handedness- and sex-weighted group of TD peers (n = 60). Secondly, their performance was also compared to matched groups of TD and hearing impaired (HI) children to evaluate the involvement of HI. The protocol comprises cognitive tests assessing response inhibition, emotion recognition, visuospatial memory, selective and sustained attention, visual memory and visual-motor integration.Based on the results, the VI group had significantly reduced scores on 'social cognition' (p = 0.018), 'executive functions' (p < 0.01), and 'perceptual-motor functioning' (p = 0.020) compared to their TD and HI peers. For the categories 'complex attention' and 'learning and memory' no differences could be observed. Analogous to the findings of previous literature, the symptoms of a VI are often not limited to the primary functions of the system, but also comprise an impact on emotional and cognitive performance. Therefore, more holistic rehabilitation approaches should be encouraged, with a screening and attention for cognitive, emotional and behavioral dysfunctions in the vestibular population. Since this is one of the first studies to investigate the involvement of a VI in a child's cognitive development, these findings support the need for studies further characterizing the impact of a VI, the underlying pathophysiology and the effect of different rehabilitation procedures.

Interpreting the meaning of changes in hippocampal volume associated with vestibular loss

Many studies have documented cognitive deficits, especially spatial cognitive deficits, in patients with some form of vestibular loss. Almost 20 years ago, hippocampal (HPC) atrophy was reported to be correlated with spatial memory deficits in such patients and the idea has gradually emerged that HPC atrophy may be causally responsible for the cognitive deficits. However, the results of studies of HPC volume following vestibular loss have not always been consistent, and a number of studies have reported no evidence of HPC atrophy. This paper argues that HPC atrophy, if it does occur following vestibular loss, may not be directly, causally responsible for the cognitive deficits, and that it is more likely that rapid functional changes in the HPC are responsible, due to the interruption of the transmission of vestibular information to the HPC. The argument presented here rests on 3 tranches of evidence: (1) Cognitive deficits have been observed in humans even in the absence of HPC atrophy; (2) HPC atrophy has not been reported in animal studies following vestibular loss, despite cognitive deficits; and (3) Animal studies have shown that the interruption of the transmission of vestibular information to the HPC has immediate consequences for HPC place cells, far too quickly to be explained by HPC atrophy. It is possible that HPC atrophy, when it does occur, is related to the longer-term consquences of living with vestibular loss, which are likely to increase circulating cortisol.

[Animal models of balance pathologies: New tools to study peripheral vestibulopathies]

The different types of peripheral vestibulopathies (PVs) or peripheral vestibular disorders (PVDs) are essentially diagnosed on the basis of their clinical expression. The heterogeneity of vestibular symptoms makes it difficult to stratify patients for therapeutic management. Animal models of PVs are a good mean to search for clinical evaluation criteria allowing to objectively analyze the kinetics of expression of the vertigo syndrome and to evaluate the benefits of therapeutic strategies, whether they are pharmacological or rehabilitative. The question of the predictability of these animal models is therefore crucial for the identification of behavioral and biological biomarkers that could then be used in the human clinic. In this review, we propose an overview of the different animal models of PVs, and discuss their relevance for the understanding of the underlying pathophysiological mechanisms and the development of new and more targeted therapeutic approaches.

Association of Bilateral Vestibulopathy With and Without Hearing Loss With Cognitive-Motor Interference

Importance

The past years, evidence suggested that the primary symptoms traditionally associated with bilateral vestibulopathy (BV) do not represent the full picture of this patient population. Recent literature also demonstrated cognitive impairment. However, although multitasking and dual-tasking are widely present in everyday activities, most of these studies assessed cognitive function only in single-task conditions.

Objective

To uncover the association of BV with and without hearing loss with cognitive and motor performance and cognitive-motor interference.

Design, Setting, and Participants

This prospective case-control study assessed persons with an isolated BV and persons with BV and a concomitant hearing loss compared with a healthy control group. Data were analyzed in December 2022. The study was conducted at Ghent University (Ghent, Belgium). Data collection took place between March 26, 2021, and November 29, 2022.

Main Outcomes and Measures

All participants completed the 2BALANCE dual-task protocol, comprising a static and a dynamic motor task that was combined with 5 visual cognitive tasks. These cognitive tasks assessed mental rotation, visuospatial memory, working memory, response inhibition (executive function), and processing speed. All cognitive tasks were performed in a single-task condition (while seated) and in a dual-task condition (combined with a static and a dynamic motor task). The static task comprised balancing on a force platform with foam pad, and the dynamic task comprised walking at a self-selected speed on the GAITRite Walkway. Both motor tasks were performed in the single-task and dual-task condition.

Results

Nineteen persons with BV and hearing loss (mean [SD] age, 56.70 [10.12] years; 10 women [52.6%]), 22 persons with an isolated BV (mean [SD] age, 53.66 [13.35] years; 7 women [31.8%]), and 28 healthy control participants were included (mean [SD] age, 53.73 [12.77] years; 12 women [42.9%]). Both patient groups had mental rotation and working memory impairment in a single-task condition and slower processing speed when walking (ie, during the dynamic dual-task condition). Additionally, the patient group with hearing loss had impaired visuospatial memory and executive function deficits in single-task and dual-task conditions, while this could only be elicited when performing a motor task in persons with isolated BV (ie, when dual-tasking).

Conclusion and Relevance

The findings of this case-control study suggest an association between vestibular function and cognitive and motor performance, even greater in persons with a concomitant hearing loss than in persons with an isolated BV.

Accelerated Cognitive Decline Associated With Hearing Loss and Bilateral Vestibulopathy: Insights From a Prospective Cross-Sectional Study Using the Repeatable Battery for the Assessment of Neuropsychological Status Adjusted for the Hearing Impaired in the DFNA9 Population

BACKGROUND

DeaFNess Autosomal dominant 9 (DFNA9) is a hereditary disorder known to affect both hearing and vestibular function in its carriers. Its phenotype is characterized by progressive sensorineural hearing loss (SNHL) and vestibular dysfunction evolving towards bilateral vestibulopathy (BV) by the 3rd to 5th life decade. Recent studies have identified the impact of hearing loss and vestibular dysfunction on cognitive functioning.

OBJECTIVE

The main objective of this study was to investigate how the cognitive functioning of carriers of the p.Pro51Ser variant in the COCH gene is affected by the disease and compare these results with a matched healthy control group.

STUDY DESIGN

Forty-six carriers of the pathogenic p.Pro51Ser variant in the COCH gene were included in this study, of which 38 met the Bárány Society criteria and were thus diagnosed with BV. All subjects were between the age of 22 and 72 years old. Each control was individually matched based on age, gender, and education level. A cognitive, vestibular, and hearing assessment was performed in all subjects. All participants completed the Repeatable Battery for the Assessment of Neuropsychological Status, adjusted for the Hearing Impaired (RBANS-H), a cognitive test battery that includes subtests probing Immediate and Delayed Memory, Visuospatial/Constructional, Language, and Attention.

RESULTS

Overall, the DFNA9 patients demonstrated significantly lower scores on the Immediate Memory subscale and lower Total Scale scores than their healthy matched controls. The total sample was divided into two groups: age <55 years old and age ≥55 years old. The DFNA9 group aged ≥55 years old obtained significantly lower scores on the Attention subscale and lower Total Scale scores than their matched controls. Cognition of DFNA9 patients aged <55 years old no longer differed significantly from their matched controls.

CONCLUSION

This cross-sectional study found that DFNA9 patients demonstrated cognitive deficits in comparison with their healthy matched controls. The DFNA9 group aged ≥ 55 years old obtained significantly lower scores on the Total Scale and Attention subscale. This finding; however, was not observed for the age group younger than 55 years old. Further research is needed on the individual trajectory of SNHL and vestibular function, and how hearing rehabilitation affects cognitive functioning.

Association between hearing loss and trauma based on population data of Korea

BACKGROUND

Although several studies have been conducted to assess the association between hearing loss (HL) and trauma, no studies have analyzed trauma comprehensively based on population-based data.

OBJECTIVES

To investigate the association between HL and trauma in daily life using National Health Insurance Service National Sample Cohort data of Korea.

MATERIALS AND METHODS

People who were registered with severe or mild hearing disability by the Korean government from 2002 to 2015, were included in this study. Trauma was defined as an outpatient visit or admission under diagnostic codes associated with trauma. The risk for trauma was analyzed using multiple logistic regression model.

RESULTS

There were 5,114 subjects in the mild hearing disability group and 1,452 in the severe hearing disability group. The risk for trauma was significantly higher in the mild and severe hearing disability groups than in the control group. The risk was higher in the mild hearing disability group than in the severe hearing disability group.

CONCLUSIONS AND SIGNIFICANCE

Individuals with hearing disability are at a higher risk for trauma based on population-based data in Korea, which indicates that HL increases the risk for trauma.

Spatial orientation, postural control and the vestibular system in healthy elderly and Alzheimer's dementia

Background

While extensive research has been advancing our understanding of the spatial and postural decline in healthy elderly (HE) and Alzheimer's disease (AD), much less is known about how the vestibular system contributes to the spatial and postural processing in these two populations. This is especially relevant during turning movements in the dark, such as while walking in our garden or at home at night, where the vestibular signal becomes central. As the prevention of falls and disorientation are of serious concern for the medical service, more vestibular-driven knowledge is necessary to decrease the burden for HE and AD patients with vestibular disabilities.

Overview of the article

The review briefly presents the current "non-vestibular based" knowledge (i.e. knowledge based on research that does not mention the "vestibular system" as a contributor or does not investigate its effects) about spatial navigation and postural control during normal healthy ageing and AD pathology. Then, it concentrates on the critical sense of the vestibular system and explores the current expertise about the aspects of spatial orientation and postural control from a vestibular system point of view. The norm is set by first looking at how healthy elderly change with age with respect to their vestibular-guided navigation and balance, followed by the AD patients and the difficulties they experience in maintaining their balance or during navigation.

Conclusion

Vestibular spatial and vestibular postural deficits present a considerable disadvantage and are felt not only on a physical but also on a psychological level by all those affected. Still, there is a clear need for more (central) vestibular-driven spatial and postural knowledge in healthy and pathological ageing, which can better facilitate our understanding of the aetiology of these dysfunctions. A possible change can start with the more frequent implementation of the "vestibular system examination/rehabilitation/therapy" in the clinic, which can then lead to an improvement of future prognostication and disease outcome for the patients.

What Predictability for Animal Models of Peripheral Vestibular Disorders?

The different clinical entities grouped under the term peripheral vestibulopathies (PVs) or peripheral vestibular disorders (PVDs) are distinguished mainly based on their symptoms/clinical expression. Today, there are very few commonly accepted functional and biological biomarkers that can confirm or refute whether a vestibular disorder belongs to a precise classification. Consequently, there is currently a severe lack of reliable and commonly accepted clinical endpoints, either to precisely follow the course of the vertigo syndrome of vestibular origin or to assess the benefits of therapeutic approaches, whether they are pharmacological or re-educational. Animal models of PV are a good means to identify biomarkers that could subsequently be exploited in human clinical practice. The question of their predictability is therefore crucial. Ten years ago, we had already raised this question. We revisit this concept today in order to take into account the animal models of peripheral vestibular pathology that have emerged over the last decade, and the new technological approaches available for the behavioral assessment of vestibular syndrome in animals and its progression over time. The questions we address in this review are the following: are animal models of PV predictive of the different types and stages of vestibular pathologies, and if so, to what extent? Are the benefits of the pharmacological or reeducational therapeutic approaches achieved on these different models of PV (in particular the effects of attenuation of the acute vertigo, or acceleration of central compensation) predictive of those expected in the vertiginous patient, and if so, to what extent?

Bioinspired Artificial Motion Sensory System for Rotation Recognition and Rapid Self-Protection

As one of the most common synergies between the exteroceptors and proprioceptors, the synergy between visual and vestibule enables the human brain to judge the state of human motion, which is essential for motion recognition and human self-protection. Hence, in this work, an artificial motion sensory system (AMSS) based on artificial vestibule and visual is developed, which consists of a tribo-nanogenerator (TENG) as a vestibule that can sense rotation and synaptic transistor array as retina. The principle of temporal congruency has been successfully realized by multisensory input. In addition, pattern recognition results show that the accuracy of multisensory integration is more than 15% higher than that of single sensory. Moreover, due to the rotation recognition and visual recognition functions of AMSS, we realized multimodal information recognition including angles and numbers in the spiking correlated neural network (SCNN), and the accuracy rate reached 89.82%. Besides, the rapid self-protection of a human was successfully realized by AMSS in the case of simulated amusement rides, and the reaction time of multiple motion sensory integration is only one-third of that of a single vestibule. The development of AMSS based on the synergy of simulated vision and vestibule will show great potential in neural robot, artificial limbs, and soft electronics.

Recent developments in the understanding of the interactions between the vestibular system, memory, the hippocampus, and the striatum

Over the last two decades, evidence has accumulated to demonstrate that the vestibular system has extensive connections with areas of the brain related to spatial memory, such as the hippocampus, and also that it has significant interactions with areas associated with voluntary motor control, such as the striatum in the basal ganglia. In fact, these functions are far from separate and it is believed that interactions between the striatum and hippocampus are important for memory processing. The data relating to vestibular-hippocampal-striatal interactions have considerable implications for the understanding and treatment of Alzheimer's Disease and Parkinson's Disease, in addition to other neurological disorders. However, evidence is accumulating rapidly, and it is difficult to keep up with the latest developments in these and related areas. The aim of this review is to summarize and critically evaluate the relevant evidence that has been published over the last 2 years (i.e., since 2021), in order to identify emerging themes in this research area.

Evidence for cognitive impairment in patients with vestibular disorders

OBJECTIVE

 Extensive animal research has shown that vestibular damage can be associated with cognitive deficits. More recently, new evidence has emerged linking vestibular disorders to cognitive impairment in humans. Herein, we review contemporary research on the pathophysiology of cognitive-vestibular interactions and discuss its emerging clinical relevance.

DATA SOURCES

PubMed, Embase, and Cochrane databases.

REVIEW METHODS

A systematic literature search was performed with combinations of search terms: "cognition," "cognitive impairment," "chronic fatigue," "brain fog," "spatial navigation," "attention," "memory," "executive function," "processing speed," and "vestibular hypofunction." Relevant articles were considered for inclusion, including basic and clinical studies, case series, and major reviews.

CONCLUSIONS

Patients with vestibular disorders can demonstrate long-term deficits in both spatial and nonspatial cognitive domains. The underlying mechanism(s) linking the vestibular system to cognitive function is not well characterized, but several neuro-biologic correlates have been identified. Additional screening tools are required to identify individuals at risk for cognitive impairment, and further research is needed to determine whether treatment of vestibular dysfunction has the capacity to improve cognitive function.

IMPLICATIONS FOR PRACTICE

Physicians should be aware of emerging data supporting the presence of cognitive deficits in patients with vestibular disorders. Prevention and treatment of long-term cognitive deficits may be possible through screening and rehabilitation.

Associations of Bilateral Vestibulopathy With Cognition in Older Adults Matched With Healthy Controls for Hearing Status

Question

Is bilateral vestibulopathy (BV) associated with cognitive function in older adults?

Findings

In this cross-sectional study including 34 participants with BV and 34 age-, sex-, and hearing performance–matched controls, participants with BV had worse cognitive function in general, which was most pronounced in the subdomains of immediate memory, visuospatial cognition, and attention.

Meaning

These findings support existing evidence on an association between vestibular loss and cognitive impairment.

Importance

Recent literature suggests there may be a significant effect of the vestibular system on cognition and visuospatial processing. Given the increasing prevalence of dementia and individuals at risk for it, exploring possible modifiable risk factors, including vestibular dysfunction, is vital.

Objectives

To explore the association of bilateral vestibulopathy (BV) with cognitive function in older adults, taking hearing status into account, and to explore multiple vestibular characteristics and their potential associations with cognition in patients with BV.

Design, Setting, and Participants

This cross-sectional study assessed older adults (age 55-84 years) with diagnosed BV from a single center using baseline measurements from the Gehoor, Evenwicht en Cognitie (GECKO) study, an ongoing prospective longitudinal cohort study. Each participant was individually matched with a healthy control based on age, sex, and hearing performance. Data were analyzed in January 2022.

Main Outcomes and Measures

The primary outcome measure was cognition, measured by the Repeatable Battery for the Assessment of Neuropsychological Status for Hearing-Impaired Individuals (RBANS-H).

Results

A total of 68 patients were assessed, including 34 patients with BV (mean [SD] age, 63.3 [6.0] years; 18 [53%] men) matched with 34 control individuals without BV. Overall, participants with BV had a clinically meaningful lower score on the RBANS-H total scale compared with those without BV (mean [SD] score, 98.62 [12.70] vs 105.91 [11.03]). This decline was most pronounced in the subdomains of immediate memory (mean [SD] score, 107.74 [10.66] vs 112.26 [10.66]), visuospatial cognition (mean [SD] score, 90.06 [13.34] vs 100.47 [13.91]), and attention (mean [SD] score, 94.79 [16.39] vs 102.06 [12.97]). There were no differences in language or delayed memory subdomains. Within the BV population, 1 vestibular parameter (the Performance-Oriented Mobility Assessment, in particular the balance subscale) was associated with lower cognitive scores (r₃₂ = 0.51; 95% CI, 0.20 to 0.72; η² = 0.26). Other vestibular parameters, including measurements of the peripheral vestibular end organ and questionnaires, showed no association.

Conclusions and Relevance

These findings suggest there was an association between vestibular loss and cognitive impairment. Further research on the causal mechanisms underlying this association and the possible impact of vestibular rehabilitation on cognition is needed.

Resting-State Electroencephalography and P300 Evidence: Age-Related Vestibular Loss as a Risk Factor Contributes to Cognitive Decline

Background:

In recent years, there have been several meaningful advances in the understanding of the cognitive effects of vestibular loss. However, there has not yet been an investigation exploring the early biomarkers of preclinical cognitive decline in individuals with age-related vestibular loss.

Objective:

We aim to explore the “early biomarkers” of preclinical cognitive decline based on altered cortical activity (resting-state electroencephalography (EEG) and P300) with a multichannel EEG system in individuals with age-related vestibular loss.

Method:

This is a case-control study. A total of 21 patients with age-related vestibular loss (66.50±5.79 years, 13 [62% ] females), 19 patients with cognitive decline (68.42±5.82 years, 13 [68% ] females), and 21 age- and sex-matched healthy controls were recruited. All participants underwent a comprehensive battery of neuropsychological tests, audio-vestibular evaluations, resting-state EEG and P300 recordings.

Results:

Significant visuo-spatial, executive, and attention hypofunction were observed in the age-related vestibular group, reflected by decreased subscale scores. Reduced gamma functional connectivity between the right cuneus (Brodmann area 19, BA19) and the left superior parietal gyrus (BA7) was observed in both the age-related vestibular group and the cognitive impairment group. Smaller P300 amplitudes were observed in the age-related vestibular group (1.43±3.69μV) and cognitive impairment group (1.15±4.24μV) than in the healthy control group (3.97±2.38μV).

Conclusion:

Decreased P300 amplitude and functional connectivity between the right BA19 and the left BA7 were “early biomarkers” observed in individuals with age-related vestibular loss; these biomarkers may contribute to visuospatial, executive, and attention hypofunction.

Navigation strategies in patients with vestibular loss tested in a virtual reality T-maze

During navigation, humans mainly rely on egocentric and allocentric spatial strategies, two different frames of reference working together to build a coherent representation of the environment. Spatial memory deficits during navigation have been repeatedly reported in patients with vestibular disorders. However, little is known about how vestibular disorders can change the use of spatial navigation strategies. Here, we used a new reverse T-maze paradigm in virtual reality to explore whether vestibular loss specifically modifies the use of egocentric or allocentric spatial strategies in patients with unilateral (n = 23) and bilateral (n = 23) vestibular loss compared to healthy volunteers (n = 23) matched for age, sex and education level. Results showed that the odds of selecting and using a specific strategy in the T-maze were significantly reduced in both unilateral and bilateral vestibular loss. An exploratory analysis suggests that only right vestibular loss decreased the odds of adopting a spatial strategy, indicating an asymmetry of vestibular functions. When considering patients who used strategies to navigate, we observed that a bilateral vestibular loss reduced the odds to use an allocentric strategy, whereas a unilateral vestibular loss decreased the odds to use an egocentric strategy. Age was significantly associated with an overall lower chance to adopt a navigation strategy and, more specifically, with a decrease in the odds of using an allocentric strategy. We did not observe any sex difference in the ability to select and use a specific navigation strategy. Findings are discussed in light of previous studies on visuo-spatial abilities and studies of vestibulo-hippocampal interactions in peripheral vestibular disorders. We discuss the potential impact of the history of the disease (chronic stage in patients with a bilateral vestibulopathy vs. subacute stage in patients with a unilateral vestibular loss), of hearing impairment and non-specific attentional deficits in patients with vestibular disorders.

The Cognitive-Vestibular Compensation Hypothesis: How Cognitive Impairments Might Be the Cost of Coping With Compensation

Previous research in vestibular cognition has clearly demonstrated a link between the vestibular system and several cognitive and emotional functions. However, the most coherent results supporting this link come from rodent models and healthy human participants artificial stimulation models. Human research with vestibular-damaged patients shows much more variability in the observed results, mostly because of the heterogeneity of vestibular loss (VL), and the interindividual differences in the natural vestibular compensation process. The link between the physiological consequences of VL (such as postural difficulties), and specific cognitive or emotional dysfunction is not clear yet. We suggest that a neuropsychological model, based on Kahneman's Capacity Model of Attention, could contribute to the understanding of the vestibular compensation process, and partially explain the variability of results observed in vestibular-damaged patients. Several findings in the literature support the idea of a limited quantity of cognitive resources that can be allocated to cognitive tasks during the compensation stages. This basic mechanism of attentional limitations may lead to different compensation profiles in patients, with or without cognitive dysfunction, depending on the compensation stage. We suggest several objective and subjective measures to evaluate this cognitive-vestibular compensation hypothesis.

Age-Related Changes in the Cochlea and Vestibule: Shared Patterns and Processes

Both age-related hearing loss (ARHL) and age-related loss in vestibular function (ARVL) are prevalent conditions with deleterious consequences on the health and quality of life. Age-related changes in the inner ear are key contributors to both conditions. The auditory and vestibular systems rely on a shared sensory organ - the inner ear - and, like other sensory organs, the inner ear is susceptible to the effects of aging. Despite involvement of the same sensory structure, ARHL and ARVL are often considered separately. Insight essential for the development of improved diagnostics and treatments for both ARHL and ARVL can be gained by careful examination of their shared and unique pathophysiology in the auditory and vestibular end organs of the inner ear. To this end, this review begins by comparing the prevalence patterns of ARHL and ARVL. Next, the normal and age-related changes in the structure and function of the auditory and vestibular end organs are compared. Then, the contributions of various molecular mechanisms, notably inflammaging, oxidative stress, and genetic factors, are evaluated as possible common culprits that interrelate pathophysiology in the cochlea and vestibular end organs as part of ARHL and ARVL. A careful comparison of these changes reveals that the patterns of pathophysiology show similarities but also differences both between the cochlea and vestibular end organs and among the vestibular end organs. Future progress will depend on the development and application of new research strategies and the integrated investigation of ARHL and ARVL using both clinical and animal models.