Vestibular Loss in Older Adults Is Associated with Impaired Spatial Navigation: Data from the Triangle Completion Task

Investigating short latency subcortical vestibular projections in humans: what have we learned?

Vestibular evoked myogenic potentials (VEMPs) are now widely used for the noninvasive assessment of vestibular function and diagnosis in humans. This review focuses on the origin, properties, and mechanisms of cervical VEMPs and ocular VEMPs; how these reflexes relate to reports of vestibular projections to brain stem and cervical targets; and the physiological role of (otolithic) cervical and ocular reflexes. The evidence suggests that both VEMPs are likely to represent the effects of excitation of irregularly firing otolith afferents. While the air-conducted cervical VEMP appears to mainly arise from excitation of saccular receptors, the ocular VEMP evoked by bone-conducted stimulation, including impulsive bone-conducted stimuli, mainly arises from utricular afferents. The surface responses are generated by brief changes in motor unit firing. The effects that have been demonstrated are likely to represent otolith-dependent vestibulocollic and vestibulo-ocular reflexes, both linear and torsional. These observations add to previous reports of short latency otolith projections to the target muscles in the neck (sternocleidomastoid and splenius) and extraocular muscles (the inferior oblique). New insights have been provided by the investigation and application of these techniques.

The Growing Evidence for the Importance of the Otoliths in Spatial Memory

Many studies have demonstrated that vestibular sensory input is important for spatial learning and memory. However, it has been unclear what contributions the different parts of the vestibular system - the semi-circular canals and otoliths - make to these processes. The advent of mutant otolith-deficient mice has made it possible to isolate the relative contributions of the otoliths, the utricle and saccule. A number of studies have now indicated that the loss of otolithic function impairs normal spatial memory and also impairs the normal function of head direction cells in the thalamus and place cells in the hippocampus. Epidemiological studies have also provided evidence that spatial memory impairment with aging, may be linked to saccular function. The otoliths may be important in spatial cognition because of their evolutionary age as a sensory detector of orientation and the fact that velocity storage is important to the way that the brain encodes its place in space.

The effects of head rotation exercise on postural balance, muscle strength, and gait in older women

This study aimed to evaluate the effects of resistive exercise (RE) with head rotation exercise (RE+HRE) on postural balance, lower limb muscle strength, and gait in older women. This study was conducted from December 7, 2015 to January 29, 2016 in Seoul, South Korea. Forty older women were recruited at welfare center and randomly allocated to RE+HRE (n = 20) or RE (n = 20) groups. The RE+HRE group performed RE+HRE for 60 min twice per week for 6 weeks, using an elastic band with variable resistance along the length. The HRE included horizontal or vertical head movement during the exercise. The RE group performed RE in a similar manner, but without head movements. The outcome measures were static postural balance (one-leg stance test, functional reach test, and postural sway), dynamic postural balance (timed up and go test, four square step test, and Mini-balance evaluation systems test), lower limb muscle strength (sit-to-stand test), and temporal gait parameters. In the RE+HRE group, all variables were significantly improved compared to baseline (p < .05), and postural balance and gait were significantly improved compared to those in the RE group (p < .05). These findings suggest that RE+HRE can improve dynamic postural balance, gait speed, and cadence in older women.

Presbyvestibulopathy: Diagnostic criteria Consensus document of the classification committee of the Bárány Society

This paper describes the diagnostic criteria for presbyvestibulopathy (PVP) by the Classification Committee of the Bárány Society. PVP is defined as a chronic vestibular syndrome characterized by unsteadiness, gait disturbance, and/or recurrent falls in the presence of mild bilateral vestibular deficits, with findings on laboratory tests that are between normal values and thresholds established for bilateral vestibulopathy.

The diagnosis of PVP is based on the patient history, bedside examination and laboratory evaluation. The diagnosis of PVP requires bilaterally reduced function of the vestibulo-ocular reflex (VOR). This can be diagnosed for the high frequency range of the VOR with the video-HIT (vHIT); for the middle frequency range with rotary chair testing; and for the low frequency range with caloric testing.

For the diagnosis of PVP, the horizontal angular VOR gain on both sides should be < 0.8 and > 0.6, and/or the sum of the maximal peak velocities of the slow phase caloric-induced nystagmus for stimulation with warm and cold water on each side should be < 25°/s and > 6°/s, and/or the horizontal angular VOR gain should be > 0.1 and < 0.3 upon sinusoidal stimulation on a rotatory chair.

PVP typically occurs along with other age-related deficits of vision, proprioception, and/or cortical, cerebellar and extrapyramidal function which also contribute and might even be required for the manifestation of the symptoms of unsteadiness, gait disturbance, and falls. These criteria simply consider the presence of these symptoms, along with documented impairment of vestibular function, in older adults.

Cognitive Function in Acquired Bilateral Vestibulopathy: A Cross-Sectional Study on Cognition, Hearing, and Vestibular Loss

BACKGROUND

Several studies have demonstrated cognitive deficits in patients with bilateral vestibulopathy (BVP). So far, little attention has been paid to the hearing status of vestibular patients when evaluating their cognition. Given the well-established link between sensorineural hearing loss (SNHL) and cognitive decline and the high prevalence of SNHL in BVP patients, it is therefore uncertain if the cognitive deficits in BVP patients are solely due to their vestibular loss or might be, partially, explained by a concomitant SNHL.

OBJECTIVE

To evaluate the link between cognition, hearing, and vestibular loss in BVP patients.

DESIGN

Prospective cross-sectional analysis of cognitive performance in patients with BVP and control participants without vestibular loss. Both groups included subjects with a variety of hearing (dys)function. Cognition was assessed by means of the Repeatable Battery for the Assessment of Neuropsychological Status for Hearing Impaired Individuals (RBANS-H).

RESULTS

Sixty-four BVP patients were evaluated and compared with 83 control participants. For each subscale and the totale RBANS-H scale a multiple linear regression model was fitted with the following variables: vestibular loss, hearing loss, age, gender, and education. Hearing loss seemed to be associated with worse outcome on the total RBANS-H scale and subscales immediate memory and language. Vestibular loss, on the other hand, was linked to worse performance on the attention subscale of the RBANS-H. Furthermore, we did not observe a correlation between saccular function and cognition.

CONCLUSION

This study has found general cognitive deficits in a large sample size of BVP patients. Multiple linear regression models revealed that both vestibular and hearing dysfunction were associated with different subscales of the cognitive test battery, the RBANS-H. Whereas hearing loss was associated with worse performance on total RBANS-H score, immediate memory and language, vestibular loss was observed to negatively affect attention performance.

Association Between Vestibular Vertigo and Motor Vehicle Accidents: Data From the 2016 National Health Interview Survey

Recent evidence has shown that individuals with vestibular impairment have higher rates of self-reported driving difficulty compared with individuals without vestibular impairment. However, it is unknown whether individuals with vestibular impairment are more likely to be involved in motor vehicle accidents. We used data from the 2016 National Health Interview Survey of U.S. adults to evaluate whether individuals with vestibular vertigo are more likely to experience motor vehicle accidents relative to individuals without vestibular vertigo. In multivariate analysis, vestibular vertigo was associated with an over threefold increased odds of motor vehicle accidents (odds ratio, 3.5; 95% confidence interval, 1.7-7.3). This study supports an association between vestibular dysfunction and driving impairment, and provides a relative risk of motor vehicle accidents associated with vestibular vertigo that clinicians may utilize in counseling patients on the potential safety hazards of driving.

The Vestibular System and Ageing

The world's population is ageing due to increased hygiene and improved medical care. Dizziness and imbalance frequently affect the elderly and is most common among individuals over the age of 60. In this age group approximately 30% of the population experience these debilitating symptoms at some point. They contribute to falls and frailty, which often result in hospitalization causing tremendous cost for the health care systems, and increased mortality. To make the matters worse balance disorders are often complex. Physicians face the difficulty of diagnosing the patient with the exact disorder especially since each disorder may manifest differently in each patient. In addition, several treatment options exist, however, with a low level of evidence. This chapter summarizes the underlying degenerative processes of the peripheral as well as the central vestibular system, diagnostic tools, the most common balance disorders in the elderly, and possible treatment options of these disorders.

Increased Prevalence of Vestibular Loss in Mild Cognitive Impairment and Alzheimer's Disease

BACKGROUND/AIMS

Recent evidence has shown that Alzheimer's Disease (AD) patients have reduced vestibular function relative to healthy controls. In this study, we evaluated whether patients with Mild Cognitive Impairment (MCI) also have reduced vestibular function relative to controls, and compared the level of vestibular impairment between MCI and AD patients.

METHODS

Vestibular physiologic function was assessed in 77 patients (26 MCI, 51 AD) and 295 matched controls using 3 clinical vestibular tests. The association between vestibular loss and cognitive impairment was evaluated using conditional logistic regression models.

RESULTS

Individuals with vestibular impairment had a 3 to 4-fold increased odds of being in the MCI vs. control group (p-values < 0.05). MCI patients had a level of vestibular impairment that was intermediate between controls and AD.

CONCLUSION

These findings suggest a dose-response relationship between vestibular loss and cognitive status, and support the hypothesis that vestibular loss contributes to cognitive decline.

The effect of galvanic vestibular stimulation on path trajectory during a path integration task

The purpose of this study was to determine the effects of galvanic vestibular stimulation (GVS) on path trajectory and body rotation during a triangle completion task. Participants ( N = 17, female, 18-30 years) completed the triangle completion task in virtual reality using two different size triangles. GVS was delivered at three times each participant’s threshold in either the left or right direction prior to the final leg of the triangle and continued until the participant reached their final position. Whole body kinematics were collected using an NDI Optotrak motion tracking system. Results revealed a significant main effect of GVS on arrival error such that no GVS (NGVS) had significantly smaller arrival errors than when GVS was administered. There was also a significant main effect of GVS on angular error such that NGVS had significantly smaller error than GVSaway and GVStowards. There was no significant difference between GVS trials in path variability during the final leg on route to the final position. These results demonstrate that vestibular perturbation reduced the accuracy of the triangle completion task, affecting path trajectory and body position during a path integration task in the absence of visual cues.

Relationship between vestibular sensitivity and multisensory temporal integration

A single event can generate asynchronous sensory cues due to variable encoding, transmission, and processing delays. To be interpreted as being associated in time, these cues must occur within a limited time window, referred to as a "temporal binding window" (TBW). We investigated the hypothesis that vestibular deficits could disrupt temporal visual-vestibular integration by determining the relationships between vestibular threshold and TBW in participants with normal vestibular function and with vestibular hypofunction. Vestibular perceptual thresholds to yaw rotation were characterized and compared with the TBWs obtained from participants who judged whether a suprathreshold rotation occurred before or after a brief visual stimulus. Vestibular thresholds ranged from 0.7 to 16.5 deg/s and TBWs ranged from 13.8 to 395 ms. Among all participants, TBW and vestibular thresholds were well correlated ( R² = 0.674, P < 0.001), with vestibular-deficient patients having higher thresholds and wider TBWs. Participants reported that the rotation onset needed to lead the light flash by an average of 80 ms for the visual and vestibular cues to be perceived as occurring simultaneously. The wide TBWs in vestibular-deficient participants compared with normal functioning participants indicate that peripheral sensory loss can lead to abnormal multisensory integration. A reduced ability to temporally combine sensory cues appropriately may provide a novel explanation for some symptoms reported by patients with vestibular deficits. Even among normal functioning participants, a high correlation between TBW and vestibular thresholds was observed, suggesting that these perceptual measurements are sensitive to small differences in vestibular function. NEW & NOTEWORTHY While spatial visual-vestibular integration has been well characterized, the temporal integration of these cues is not well understood. The relationship between sensitivity to whole body rotation and duration of the temporal window of visual-vestibular integration was examined using psychophysical techniques. These parameters were highly correlated for those with normal vestibular function and for patients with vestibular hypofunction. Reduced temporal integration performance in patients with vestibular hypofunction may explain some symptoms associated with vestibular loss.

Vestibular Function and Hippocampal Volume in the Baltimore Longitudinal Study of Aging (BLSA)

OBJECTIVE

This study evaluated whether reduced vestibular function in aging adults is associated with lower hippocampal volume.

STUDY DESIGN

Cross-sectional study.

SETTING

Baltimore Longitudinal Study of Aging, a long-running longitudinal cohort study of healthy aging.

PATIENTS

Eligible participants were aged ≥ 60 years and had both vestibular physiological testing and brain magnetic resonance imaging at the same visit.

INTERVENTION

Vestibular function testing consisted of the cervical vestibular-evoked myogenic potential (cVEMP) to assess saccular function, ocular VEMP to assess utricular function, and video head-impulse testing to assess the horizontal semicircular canal vestibulo-ocular reflex.

MAIN OUTCOME MEASURE

Hippocampal volume calculated using diffeomorphometry.

RESULTS

The study sample included 103 participants (range of 35-90 participants in subanalyses) with mean (±SD) age 77.2 years (±8.71). Multivariate linear models including age, intracranial volume, sex, and race showed that 1 μV amplitude increase of cVEMP was associated with an increase of 319.1 mm (p = 0.003) in mean hippocampal volume. We did not observe a significant relationship between ocular VEMP amplitude or vestibulo-ocular reflex gain and mean hippocampal volume.

CONCLUSIONS

Lower cVEMP amplitude (i.e., reduced saccular function) was significantly associated with lower mean hippocampal volume. This is in line with previous work demonstrating a link between saccular function and spatial cognition. Hippocampal atrophy may be a mechanism by which vestibular loss contributes to impaired spatial cognition in older adults. Future work using longitudinal data will be needed to evaluate the causal nature of the association between vestibular loss and hippocampal atrophy.

Saccular Impairment in Alzheimer's Disease Is Associated with Driving Difficulty

BACKGROUND/AIMS

Patients with Alzheimer's disease (AD) experience increased rates of vestibular loss. Recent studies suggest that saccular impairment in mild cognitive impairment (MCI) and AD patients is associated with impaired spatial cognitive function. However, the impact of saccular impairment on everyday behaviors that rely on spatial cognitive function is unknown.

METHODS

We recruited 60 patients (21 MCI and 39 AD) from an interdisciplinary Memory Clinic. Saccular function was measured, and a visuospatial questionnaire was administered to assess whether participants experienced impairments in terms of driving difficulty, losing objects, falls, and fear of falling.

RESULTS

In multiple logistic regression analyses, MCI and AD patients with bilateral saccular impairment had a significant, greater than 12-fold odds of driving difficulty (OR 12.1, 95% CI 1.2, 117.7) compared to MCI and AD patients with normal saccular function, and the association appears to be mediated by spatial cognition as measured by the Money Road Map Test.

CONCLUSION

This study suggests a novel link between saccular impairment and driving difficulty in MCI and AD patients and demonstrates that driving difficulty may be a real-world manifestation of impaired spatial cognition associated with saccular impairment.

Vestibular Dysfunction and Difficulty with Driving: Data from the 2001-2004 National Health and Nutrition Examination Surveys

BACKGROUND AND OBJECTIVE

There is growing understanding of the role of vestibular function in spatial navigation and orientation. Individuals with vestibular dysfunction demonstrate impaired performance on static and dynamic tests of spatial cognition, but there is sparse literature characterizing how these impairments might affect individuals in the real-world. Given the important role of visuospatial ability in driving a motor vehicle, we sought to evaluate whether individuals with vestibular dysfunction might have increased driving difficulty.

MATERIALS AND METHODS

We used data from the 2001-2004 National Health and Nutrition Examination Surveys to evaluate the influence of vestibular dysfunction in driving difficulty in a nationally representative sample of U.S. adults aged ≥50 years (n = 3,071). Vestibular function was measured with the modified Romberg test. Furthermore, since vestibular dysfunction is a known contributor to falls risk, we assessed whether individuals with vestibular dysfunction and concomitant driving difficulty were at an increased risk of falls.

RESULTS

In multivariate analyses, vestibular dysfunction was associated with a twofold increased odd of driving difficulty (odds ratio 2.16, 95% CI 1.57, 2.98). Among participants with vestibular dysfunction, concomitant driving difficulty predicted an increased risk of falls that was significantly higher than in participants with vestibular dysfunction only (odds ratio 13.01 vs. 2.91, p < 0.0001).

CONCLUSION

This study suggests that difficulty driving may be a real-world manifestation of impaired spatial cognition associated with vestibular loss. Moreover, driving difficulty may be a marker of more severe vestibular dysfunction.