Ageing-related changes in the cortical processing of otolith information in humans

Gravity perception disturbance in patients with unilateral Meniere disease

Objective

To investigate gravity perception disturbance (GPD) in patients with Meniere disease (MD), we classified GPD type based on the results of the head-tilt perception gain (HTPG) and the head-upright subjective visual vertical (HU-SVV) evaluated by the head-tilt SVV (HT-SVV) test in patients with unilateral MD.

Methods

We conducted the HT-SVV test on 115 patients with unilateral MD and 115 healthy controls. Among the 115 patients, the period from the first vertigo episode to the examination (PFVE) was known for 91 patients.

Results

The HT-SVV test classified 60.9% and 39.1% of patients with unilateral MD as GPD and non-GPD, respectively. GPD was classified according to HTPG/HU-SVV combinations as follows: Type A GPD (21.7%, normal HTPG/abnormal HU-SVV), Type B GPD (23.5%, abnormal HTPG/normal HU-SVV), and Type C GPD (15.7%, abnormal HTPG/abnormal HU-SVV). As the PFVE became longer, patients with non-GPD and Type A GPD decreased; however, those with Types B and C GPD increased.

Conclusion

This study provides novel information on unilateral MD from the perspective of gravity perception by classifying GPD based on the results of the HT-SVV test. This study's findings suggest that overcompensation for vestibular dysfunction in patients with unilateral MD exhibited by large HTPG abnormalities may be strongly associated with persistent postural-perceptual dizziness.

Level of Evidence

3b.

Chronic vestibular syndromes in the elderly: Presbyvestibulopathy - an isolated clinical entity?

BACKGROUND

Recently, the Classification Committee of the Bárány Society defined the new syndrome of "presbyvestibulopathy" for elderly patients with chronic vestibular symptoms due to a mild bilateral peripheral vestibular hypofunction. However, control of stance and gait requires multiple functioning systems, e.g. the somatosensory, visual, auditory, musculoskeletal and cardio- and cerebrovascular system. The aim of this cross-sectional database-driven study was to evaluate the frequency and characteristics of presbyvestibulopathy and additional gait relevant comorbidities.

METHODS

In total 707 patients ≥ 60 years with chronic vertigo/dizziness were admitted to our tertiary hospital and received detailed neurological, neuroorthoptic and laboratory audio-vestibular examination. Medical history, comorbidities, functional impairment and quality of life (DHI, EQ-5D-3L, VAP) were compared between presbyvestibulopathy and bilateral vestibulopathy in a matched-paired study.

RESULTS

In 95.5% of patients, complaints were better accounted for by another vestibular, neurological, cardiac or psychiatric disease and 32 patients (4.5%) met the diagnostic criteria for presbyvestibulopathy. Out of these 32 patients, the majority showed further relevant comorbidities in other sensorimotor systems. Only one patient out of 707 had "isolated" presbyvestibulopathy (0.14%). The mean total DHI scores indicated lower moderate impairment in presbyvestibulopathy than in bilateral vestibulopathy (40.6 vs. 49.0), which was confirmed by significant differences in the matched-paired analysis (p < 0.001).

CONCLUSIONS

Isolated presbyvestibulopathy is a very rare entity. It is regularly accompanied by other multisensory dysfunctions. These results indicate a potential role of mild vestibular hypofunction as a co-factor in multifactorial impairment. Thus, patients should be treated in an interdisciplinary setting aware of diverse comorbidities.

Effect of head roll-tilt on the subjective visual vertical in healthy participants: Towards better clinical measurement of gravity perception

OBJECTIVE

Gravity perception is an essential function for spatial orientation and postural stability; however, its assessment is not easy. We evaluated the head-tilt perception gain (HTPG, that is, mean perceptual gain [perceived/actual tilt angle] during left or right head roll-tilt conditions) and head-upright subjective visual vertical (SVV) using a simple method developed by us to investigate the characteristics of gravity perception in healthy participants.

METHODS

We measured the SVV and head roll-tilt angle during head roll-tilt within ±30° of vertical in the sitting and standing positions while the participant maintained an upright trunk (sitting, 434 participants; standing, 263 participants). We evaluated the head-upright SVV, HTPG, and laterality of the HTPG.

RESULTS

We determined the reference ranges of the absolute head-upright SVV (<2.5°), HTPG (0.80-1.25), and HTPG laterality (<10%) for the sitting position. The head-upright SVV and HTPG laterality were not influenced by sex or age. However, the HTPG was significantly greater in women than in men and in middle-aged (30-64 years) and elderly (65-88 years) participants than in young participants (18-29 years). The HTPG, but not the head-upright SVV or HTPG laterality, was significantly higher in the standing vs sitting position.

CONCLUSION

The HTPG is a novel parameter of gravity perception involving functions of the peripheral otolith and neck somatosensory systems to the central nervous system. The HTPG in healthy participants is influenced by age and sex in the sitting position and immediately increases after standing to reinforce the righting reflex for unstable posture, which was not seen in the head-upright SVV, previously considered the only parameter.

LEVEL OF EVIDENCE

4.

Direct comparison of activation maps during galvanic vestibular stimulation: A hybrid H2[15 O] PET-BOLD MRI activation study

Previous unimodal PET and fMRI studies in humans revealed a reproducible vestibular brain activation pattern, but with variations in its weighting and expansiveness. Hybrid studies minimizing methodological variations at baseline conditions are rare and still lacking for task-based designs. Thus, we applied for the first time hybrid 3T PET-MRI scanning (Siemens mMR) in healthy volunteers using galvanic vestibular stimulation (GVS) in healthy volunteers in order to directly compare H₂¹⁵O-PET and BOLD MRI responses. List mode PET acquisition started with the injection of 750 MBq H₂¹⁵O simultaneously to MRI EPI sequences. Group-level statistical parametric maps were generated for GVS vs. rest contrasts of PET, MR-onset (event-related), and MR-block. All contrasts showed a similar bilateral vestibular activation pattern with remarkable proximity of activation foci. Both BOLD contrasts gave more bilateral wide-spread activation clusters than PET; no area showed contradictory signal responses. PET still confirmed the right-hemispheric lateralization of the vestibular system, whereas BOLD-onset revealed only a tendency. The reciprocal inhibitory visual-vestibular interaction concept was confirmed by PET signal decreases in primary and secondary visual cortices, and BOLD-block decreases in secondary visual areas. In conclusion, MRI activation maps contained a mixture of CBF measured using H₂¹⁵O-PET and additional non-CBF effects, and the activation-deactivation pattern of the BOLD-block appears to be more similar to the H₂¹⁵O-PET than the BOLD-onset.

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.

Postural responses of galvanic vestibular stimulation: comparison between groups of older adults and young people

Abstract Objective: To evaluate the effect of vestibular manipulation on the postural sway and muscle activation of younger and older adults. Methods: The study analyzed the effects of three intensity levels of galvanic vestibular stimulation (GVS) (0.3; 0.6 and 1m) on the pattern of muscle activity and center of pressure (CP) displacements of 12 older adults (EG) and 12 young adults (CG) while maintaining their balance on a stable surface, with no vision. Results: The EG showed a positive correlation between CP displacement and muscle activity and GVS intensity. On the other hand, the magnitude of postural response in the EG was not modulated in accordance with GVS intensities. Additionally, during the highest GVS intensity level (1 mA) greater muscle activity was used to increase stiffness, decrease the amplitude of oscillation and ensure stability. This unusual response characterizes a pattern of co-activation and is perhaps a safety mechanism to ensure stability. Conclusion: The EG individuals were not able to select the appropriate motor strategy to efficiently compensate the effects of GVS. This unusual strategy reflects deficits in the vestibular system of older adults, a fact which negatively interferes with their ability to reevaluate sensory information.

Assessment of vestibular function in elderly patients

PURPOSE OF REVIEW

Individuals over the age of 60 are at an increased risk of falls, even if they do not have an isolated dysfunction of the vestibular system. The aim of this article is to review the various vestibular testing currently available and its usefulness in determining the presence of vestibular dysfunction in the elderly population. The primary vestibular tests to be reviewed include: balance function testing, vestibular evoked myogenic potentials (VEMPs), and video head impulse testing (vHIT).

RECENT FINDINGS

Balance function testing is important as it evaluates the integration of vestibular information along with sensory and visual information, which may also be impaired. VEMP testing provides a small diagnostic yield as most elderly patients have absent or reduced responses. vHIT gain is reduced in this population, but will still be within the normal range for individuals with normal balance function.

SUMMARY

The combination of various vestibular tests provides complimentary information instead of redundant information on the patient's balance function. Each test evaluates various aspects of the vestibular system which are all needed to determine stable balance in the elderly population.