Detection of human utricular otoconia degeneration in vital specimen and implications for benign paroxysmal positional vertigo

Low vitamin D and uric acid status in patients with benign paroxysmal positional vertigo

PURPOSE

Growing evidence reported that vitamin D and uric acid metabolism played roles in the occurrence of benign paroxysmal positional vertigo, an otoconia-related vestibular disorder. We aimed to investigate the serum 25-hydroxy vitamin D (25(OH)D) and uric acid in patients with benign paroxysmal positional vertigo and to determine the risk factor for benign paroxysmal positional vertigo.

METHODS

This case-control study comprised 182 patients with benign paroxysmal positional vertigo and 182 age- and gender-matched controls. All subjects' age, body mass index, systolic blood pressure, diastolic blood pressure, 25-hydroxyvitamin D (25(OH)D), uric acid and serum calcium measurements were analyzed.

RESULTS

We found a female preponderance of benign paroxysmal positional vertigo patients, with a median of 60 (52-66) years old. The results showed low vitamin D status both in benign paroxysmal positional vertigo and controls, with no significant difference of 25(OH)D levels between benign paroxysmal positional vertigo patients and controls (P > 0.05). Compared with the control group, patients with benign paroxysmal positional vertigo had a higher prevalence of vitamin D deficiency and a lower prevalence of vitamin D sufficiency (P < 0.05). Uric acid was significantly lower in the benign paroxysmal positional vertigo groups (P < 0.05). Logistic regression analysis revealed that age and uric acid were considered higher risk predictors for benign paroxysmal positional vertigo.

CONCLUSION

Our study observed low vitamin D status in patients with benign paroxysmal positional vertigo, with no significant differences of the 25(OH)D level in patients with benign paroxysmal positional vertigo and controls. Elderly, vitamin D deficiency and low uric acid levels may be risk factors for benign paroxysmal positional vertigo occurrence.

Otoconial Degeneration After Transient Ischemia Induced by Four-Vessel Occlusion in Rats

BACKGROUND AND PURPOSE

Ischemia of the inner ear may damage the otoconia. However, no study has explored any changes in the configuration of otoconia after transient ischemia of the labyrinth.

METHODS

Nineteen 7-week-old Sprague-Dawley rats were randomly assigned to either the sham (n=5) or the experimental group (n=14). The rats in the experimental group were subjected to global ischemia for 20 minutes using a four-vessel occlusion model, and were sacrificed seven days after the procedure. The rats in the sham group were sacrificed without any procedure. The otolithic organs (utricle and saccule) were dissected out for scanning electron microscope.

RESULTS

The otolithic organs in the sham group showed their normal gross configuration with a dense clumping of otoconia with a normal hexagonal morphology and a smooth surface. The otolithic organs in the experimental group also maintained a grossly normal configuration, but each otoconia showed irregular surfaces with numerous cracks or furrows, especially in the periphery of the otoconial bed.

CONCLUSIONS

The current study showed that otoconial degeneration may occur even after transient ischemia of the labyrinth. This finding supports an association between cerebral ischemia and benign paroxysmal positional vertigo.

Otolin-1, an otolith- and otoconia-related protein, controls calcium carbonate bioinspired mineralization

BACKGROUND

Otoliths and otoconia are calcium carbonate biomineral structures that form in the inner ear of fish and humans, respectively. The formation of these structures is tightly linked to the formation of an organic matrix framework with otolin-1, a short collagen-like protein from the C1q family as one of its major constituents.

METHODS

In this study, we examined the activity of recombinant otolin-1 originating from Danio rerio and Homo sapiens on calcium carbonate bioinspired mineralization with slow-diffusion method and performed crystals characterization with scanning electron microscopy, two-photon excited fluorescence microscopy, confocal laser scanning microscopy and micro-Raman spectroscopy.

RESULTS

We show that both proteins are embedded in the core of CaCO₃ crystals that form through the slow-diffusion mineralization method. Both of them influence the morphology but do not change the polymorphic mineral phase. D.rerio otolin-1 also closely adheres to the crystal surface.

GENERAL SIGNIFICANCE

The results suggest, that otolin-1 is not a passive scaffold, but is directly involved in regulating the morphology of the resulting calcium carbonate biocrystals.

Association between otolin-1 and benign paroxysmal positional vertigo: A meta-analysis

Background

There is increasing research on the potential of inner ear proteins as serum biomarkers for the diagnosis and prognosis of various inner ear diseases. Among them, benign paroxysmal positional vertigo (BPPV) is the most common vestibular disease. Notably, otolin-1, an inner ear-specific protein, is detectable in the serum of most patients with BPPV patients. Therefore, we found a need to conduct this meta-analysis to determine the relationship between otolin-1 in serum and BPPV.

Methods

This meta-analysis was conducted by searching PubMed, EMBASE, Cochrane Library, Google Scholar, and China Network Knowledge Infrastructure databases for the eligible original studies in Chinese or English published between January 2010 and February 2022. Data were collected and pooled by using the mean differences (MDs) corresponding to 95% confidence intervals (CIs). Heterogeneity among these studies was assessed by using I² statistics and the adopted fixed or random-effect mode thereafter. Egger's and Begg's tests were also used to assess the publication bias.

Results

This meta-analysis included six articles with a total of 585 participants. Serum otolin-1 levels were remarkably increased in patients with BPPV as compared to that in healthy controls (MD: 165.38, 95% CI: 110.13-220.64, p < 0.00001). However, Egger's and Begg's tests have indicated no publication bias, and the results were reliable based on the sensitivity analysis.

Conclusion

This meta-analysis indicated that there is a higher serum level of otolin-1 in patients with BPPV than in healthy controls. Therefore, otolin-1 may serve as a biomarker for the onset of BPPV.

Dynamic changes of otolith organ function before and after repositioning in patients with benign paroxysmal positional vertigo detected by virtual reality auxiliary technology: A cohort study

Objectives

To dynamically investigate otolith function in patients with benign paroxysmal positional vertigo (BPPV) before, after, and 1 month after repositioning, and explore the possible compensation mechanisms.

Methods

Thirty-six patients confirmed with BPPV (canal lithiasis) treated in our hospital between August 2020 and March 2021, as well as 36 health controls matched for age and gender (normal control group, NC group) were enrolled. For NC group, the virtual reality (VR) auxiliary static subjective visual vertical (SVV), subjective visual horizontal (SVH), and SVV of dynamic unilateral centrifugation (DUC), were measured at inclusion. For the BPPV group, visual analog scale (VAS) was used to assess the vertigo degree, while static SVV, SVH, and DUC were performed before, after, and 1 month after repositioning. First, we compare the deviations of SVV0/SVH0° when the subject's head is in the positive position, and SVV of DUC between BPPV and NC groups before repositioning, after which we compared the deviations in SVV45, SVV90, SVH45, SVH90°, and SVV of DUC between the affected and unaffected sides before repositioning. Finally, paired t-test was used to compare the VAS score, deviations in static SVV0, SVV45, SVV90, SVH0, SVH45, and SVH90°, and deviations in SVV of DUC before, after, and 1 month after repositioning. (Here, 0, 45, and 90° refer to the angle which the center axis of head deviates from the gravity line.)

Results

SVV0 SVH0°, and SVV of DUC at 120 and 180°/s 0 significantly differed between BPPV and NC group before repositioning. The deviations in SVV45, SVV90, SVH45, SVH90°, and SVV of DUC at 120°/s-2 and 180°/s-4.5 did not significantly differ between bilateral sides in BPPV patients before repositioning. The deviation in SVH90° was significantly lower after repositioning than before. The deviation in SVH45° was significantly higher 1 month after repositioning than before. The deviation angle of SVV of DUC at 180°/s-0 was significantly lower after repositioning than before. The vertigo VAS score of patient with BPPV continued to decrease after repositioning.

Conclusion

Before repositioning, the otolithic organ function of BPPV patients was obviously impaired, with no significant difference between the healthy and affected ear. After repositioning, there was a transient recovery of otolithic organ dysfunction followed by a sustained decline to similar levels to before repositioning.

Insights into Inner Ear Function and Disease Through Novel Visualization of the Ductus Reuniens, a Seminal Communication Between Hearing and Balance Mechanisms

The sensory end-organs responsible for hearing and balance in the mammalian inner ear are connected via a small membranous duct known as the ductus reuniens (also known as the reuniting duct (DR)). The DR serves as a vital nexus linking the hearing and balance systems by providing the only endolymphatic connection between the cochlea and vestibular labyrinth. Recent studies have hypothesized new roles of the DR in inner ear function and disease, but a lack of knowledge regarding its 3D morphology and spatial configuration precludes testing of such hypotheses. We reconstructed the 3D morphology of the DR and surrounding anatomy using osmium tetroxide micro-computed tomography and digital visualizations of three human inner ear specimens. This provides a detailed, quantitative description of the DR's morphology, spatial relationships to surrounding structures, and an estimation of its orientation relative to head position. Univariate measurements of the DR, inner ear, and cranial planes were taken using the software packages 3D Slicer and Zbrush. The DR forms a narrow, curved, flattened tube varying in lumen size, shape, and wall thickness, with its middle third being the narrowest. The DR runs in a shallow bony sulcus superior to the osseus spiral lamina and adjacent to a ridge of bone that we term the "crista reuniens" oriented posteromedially within the cranium. The DR's morphology and structural configuration relative to surrounding anatomy has important implications for understanding aspects of inner ear function and disease, particularly after surgical alteration of the labyrinth and potential causative factors for Ménière's disease.

The Role of Intrinsically Disordered Proteins in Liquid–Liquid Phase Separation during Calcium Carbonate Biomineralization

Some animal organs contain mineralized tissues. These so-called hard tissues are mostly deposits of calcium salts, usually in the form of calcium phosphate or calcium carbonate. Examples of this include fish otoliths and mammalian otoconia, which are found in the inner ear, and they are an essential part of the sensory system that maintains body balance. The composition of ear stones is quite well known, but the role of individual components in the nucleation and growth of these biominerals is enigmatic. It is sure that intrinsically disordered proteins (IDPs) play an important role in this aspect. They have an impact on the shape and size of otoliths. It seems probable that IDPs, with their inherent ability to phase separate, also play a role in nucleation processes. This review discusses the major theories on the mechanisms of biomineral nucleation with a focus on the importance of protein-driven liquid–liquid phase separation (LLPS). It also presents the current understanding of the role of IDPs in the formation of calcium carbonate biominerals and predicts their potential ability to drive LLPS.

N'-terminal- and Ca2+-induced stabilization of high-order oligomers of full-length Danio rerio and Homo sapiens otolin-1

Otolin-1 is a C1q family member and a major component of the organic matrix of fish otoliths and human otoconia. To date, the protein molecular properties have not been characterized. In this work, we describe biochemical characterization and comparative studies on saccular-specific otolin-1 derived from Danio rerio and Homo sapiens. Due to the low abundance of proteins in the otoconial matrix, we developed a production and purification method for both recombinant homologues of otolin-1. Danio rerio and Homo sapiens otolin-1 forms higher-order oligomers that can be partially disrupted under reducing conditions. The presence of Ca²⁺ stabilizes the oligomers and significantly increases the thermal stability of the proteins. Despite the high sequence coverage, the oligomerization of Danio rerio otolin-1 is more affected by the reducing conditions and presence of Ca²⁺ than the human homologue. The results show differences in molecular behaviour, which may be reflected in Danio rerio and Homo sapiens otolin-1 role in otolith and otoconia formation.

Otoconia Structure After Short- and Long-Duration Exposure to Altered Gravity

Vertebrates use weight-lending otoconia in the inner ear otolith organs to enable detection of their translation during self or imposed movements and a change in their orientation with respect to gravity. In spaceflight, otoconia are near weightless. It has been hypothesized that otoconia undergo structural remodeling after exposure to weightlessness to restore normal sensation. A structural remodeling is reasoned to occur for hypergravity but in the opposite sense. We explored these hypotheses in several strains of mice within a Biospecimen Sharing Program in separate space- and ground-based projects. Mice were housed 90 days on the International Space Station, 13 days on two Shuttle Orbiter missions, or exposed to 90 days of hindlimb unloading or net 2.38 g via centrifugation. Corresponding flight habitat and standard cage vivarium controls were used. Utricular otoliths were visually analyzed using scanning electron microscopy and in selected samples before and after focused ion beam (FIB) milling. Results suggest a possible mass addition to the otoconia outer shell might occur after exposure to longer-duration spaceflight, but not short ones or hindlimb unloading. A destructive process is clearly seen after centrifugation: an ablation or thinning of the outer shell and cavitation of the inner core. This study provides a purely descriptive account of otoconia remodeling after exposures to altered gravity. The mechanism(s) underlying these processes must be identified and quantitatively validated to develop countermeasures to altered gravity levels during exploration missions.

Evaluation of retrootolithic function using galvanic vestibular-evoked myogenic potentials in patients with benign paroxysmal positional vertigo

PURPOSE

The purpose is to investigate possible vestibulopathy in patients with benign paroxysmal positional vertigo (BPPV), inner ear tests, including cervical and ocular vestibular-evoked myogenic potentials (cVEMPs and oVEMPs) via various stimulation modes, were adopted.

METHODS

Fifty BPPV patients were enrolled in this study. All patients underwent pure tone audiometry, cVEMPs, oVEMPs, and caloric tests. The recurrence status, abnormal rates of inner ear tests, and the characteristic parameters of VEMPs, such as wave latencies and amplitudes, were analyzed.

RESULTS

In affected ears, the abnormal rates of acoustic cVEMPs, vibratory oVEMPs, galvanic cVEMPs, and galvanic oVEMPs were 62%, 28%, 36%, and 14%, respectively. The abnormalities of acoustic cVEMPs were significantly larger than those of vibratory oVEMPs, and acoustic/vibratory VEMPs had significantly higher abnormal rates than the corresponding galvanic VEMPs.

CONCLUSION

BPPV patients may have both otolithic and neural dysfunctions. Otolithic organ damage occurs more frequently than retrootolithic neural degeneration, and the saccular macula might have a greater extent of damage than the utricular macula.

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.

Vestibular drop attacks in Ménière's disease: A systematic review and meta-analysis of frequency, correlates and consequences

BACKGROUND

Vestibular drop attacks (VDA), also called Tumarkin otolith crises as a complication of Ménière's disease (MD) were first described in 1936. Nevertheless, a clearer understanding of their prevalence and manifestations is needed.

THE OBJECTIVE

of this review is to determine the frequency, correlates and consequences of VDA in MD.

METHOD

Three databases were searched (i.e., MEDLINE, PubMed and Google Academia). A total of 1,791 references were identified, of which 18 studies were considered eligible. There was a large variation in the definition of VDA used in the studies.

RESULTS

The frequency of VDA in MD leading to a fall to the ground varied from 3 to 19% in 9 hospital-based studies. In studies where a less restrictive definition of VDA included attacks with postural perturbation, tripping and near-to-fall situations was used the prevalence ranged from 50 to 72%. The pooled frequency of VDA leading to fall to the ground was 8% (95% CI 4 to 12%) in hospital-based studies. In these studies, VDA often occurred in severe and advanced MD whereas in cohort studies such connection was not found. Co-morbidity with migraine increased the likelihood of VDA occurrence in MD. In 3 studies syncope was recorded in connection to VDA with falls. In terms of clinical manifestation, audiometry, MRI, vestibular evoked muscle response measures indicated endolymphatic hydrops with involvement of the otolith system. The hearing loss was more pronounced, and balance was worse in MD patients with VDA than in those without. Injury associated with VDA was reported in only one study.

CONCLUSIONS

VDA is a common phenomenon in MD, occurring even in mild MD and complicated with syncope. Some preliminary evidence suggests that VDA may lead to severe injuries.

MRI utricle diameter asymmetry is significantly greater in dogs with idiopathic vestibular syndrome compared with unaffected dogs

Idiopathic vestibular syndrome (IVS) is the most common cause of acute unilateral peripheral vestibular dysfunction in older dogs. The purpose of this retrospective, cross-sectional study was to characterize morphological changes in the utricle of dogs affected by IVS, using MRI. To evaluate differences between affected and unaffected utricles, the ratio of the largest to the smallest utricle diameter was obtained, as measured on transverse T2-weighted images, and defined as the utricle asymmetricity ratio (UAR). Out of 137 patients diagnosed with IVS after excluding other vestibular diseases by MRI, 101 were eligible for inclusion. Additionally, 31 older dogs with no signs of vestibular disorders or other intracranial diseases were included as a control group. The disease group was divided into two subgroups in which the direction of head tilt and nystagmus symptoms versus the decreased utricle diameters were consistent or inconsistent. The medians of UARs of the IVS and control groups were 0.83 (range 0.37-1.00) and 0.98 (0.70-1.00), respectively. The medians of the UARs of the consistent and inconsistent IVS subgroups were 0.82 (0.37-0.99) and 0.90 (0.74-1.00), respectively. The UAR of the IVS group was significantly decreased than that of the control group and UAR of the consistent sub-group was significantly decreased than that of the inconsistent sub-group (P < .01). In conclusion, significant asymmetry of utricle diameter was identified in dogs with IVS versus unaffected dogs. We propose that canine IVS may possibly be correlated with structural atrophy of the vestibular system.

Increased Otolin-1 in Serum as a Potential Biomarker for Idiopathic Benign Paroxysmal Positional Vertigo Episodes

Objective: Otolin-1, a main specific otoconia matrix protein, passes through the labyrinth-blood barrier and is detectable in peripheral blood. Serum otolin-1 levels differ between patients with benign paroxysmal positional vertigo (BPPV) and healthy controls and are significantly age-related, increasing in healthy controls with age, suggesting that serum otolin-1 levels reflect otolith status. The aim of this study was to determine whether otolin-1 levels change during vertigo episodes in patients with BPPV and whether any change is specific and sensitive enough for BPPV episodes.

Method: Patients diagnosed with de novo idiopathic BPPV during an acute episode were included in the study from May 2017 to May 2018. Blood samples were drawn before patients were treated with canalith-repositioning maneuvers. Serum otolin-1 levels were compared between 78 patients and 121 age- and sex-matched healthy individuals.

Results: There were no significant differences between the groups in the age distribution, sex ratio, body mass index, clinical history, routine blood parameters, or total protein, albumin, uric acid, creatinine, blood urea nitrogen and lipid profiles (P > 0.05). Serum levels of otolin-1 were significantly higher in BPPV patients than in healthy controls (P < 0.001). Receiver operating characteristic analysis revealed that a serum otolin-1 value of 299.45 pg/ml was the optimal cut-off value to discriminate patients with BPPV from healthy controls (area under the curve 0.757, 95% CI 0.687~0.826) with a sensitivity of 67.9% and a specificity of 72.7%.

Conclusion: Serum levels of otolin-1 may be a potential biomarker for BPPV episodes.

[Current aspects of vertigo and dizziness in advanced age]

Vertigo and dizziness in advanced age are common complaints in daily clinical practice. The otorhinolaryngologist holds a central position in the differential diagnostic clarification. Age-related disorders (e.g. benign positional vertigo, presbyvestibulopathy, otholith functional disorders) arise due to a physiological, individually distinct and objectively detectable reduction in the sensitivity of sensory and extrasensory elements of the vestibular system. They may reach pathological significance if these dysfunctions affect the physical and emotional well-being (e.g. gait disturbances and falls with subsequent morbidity). Disorders accompanying aging (e.g. neurological, cardiovascular or psychiatric) can occur simultaneously with age-related changes in sensory function. The identification, especially with respect to the risk of falling in older people and the development of individual therapeutic strategies is an interdisciplinary task. Besides a causative therapy, strength, coordination and balance training contribute to the treatment of equilibrium disorders and falls from the perspective of evidence-based medicine.

Evaluation of bone mineral density and 25-(OH) vitamin D levels in middle-aged and elderly women with recurrent benign paroxysmal positional vertigo

Background: Middle-aged and elderly perimenopausal women are prone to developing BPPV without definite cause. Objectives: This study aimed to investigate the correlation between bone mineral density (BMD), 25-(OH) vitamin D, and serum calcium levels in patients with benign paroxysmal positional vertigo (BPPV) in middle-aged and elderly women.Material and methods: A total of 103 women with two or more recurrent BPPV episodes (group A) and 80 age-matched healthy controls (group B) were recruited. All subjects had BMD and serum 25-(OH) D levels measurements taken, and the results were compared.Results: BMD was reduced in group A, and the proportion of osteoporosis was higher than in group B (p = .039). The BMD T-score and 25-(OH) vitamin D level were lower in group A than in group B (p = .004 and p < .0001, respectively). In group A, the BMD T-score was lower (p = .017) and serum 25-(OH) vitamin D level was higher (p < .0001) in premenopausal women than in menopausal women.Conclusions and Significance: Our study found that middle-aged and elderly women with recurrent BPPV, especially postmenopausal women, may present decreased BMD and serum vitamin D levels.

A Relationship Between Blood Levels of Otolin-1 and Vitamin D

OBJECTIVE

Low vitamin D levels have been associated with and could play a role in the pathogenesis of idiopathic benign paroxysmal positional vertigo (iBPPV). Since otoconia degeneration contributes to iBPPV and a lack of vitamin D may impact otoconia structure and integrity, we proposed a negative association between vitamin D levels and levels of a proposed circulatory biomarker for otolithic degeneration, otolin-1.

STUDY DESIGN

Cross-sectional clinical study.

SETTING

Clinical research center.

PATIENTS

Seventy-nine men and women ranging in age from 22 to 95 years old without known vertigo.

INTERVENTIONS

Diagnostic.

MAIN OUTCOME MEASURES

Blood levels of 25-OH vitamin D and otolin-1.

RESULTS

Previously, we had reported higher otolin-1 levels in older age groups. The majority of the subjects (83%) had vitamin D levels that were below 40 ng/ml. Vitamin D level was lowest in the young and increased with age before declining in subjects 70 years of age and older (p = 0.005). There was a negative correlation between vitamin D and otolin-1 levels of subjects over 70 (r = -0.36, p = 0.036).

CONCLUSION

Our results demonstrate a relationship between vitamin D and otolin-1. The majority of our subjects had abnormally low vitamin D levels, but only those over 70 years of age showed a negative correlation with high otolin-1 levels. We postulate that a seasonal drop in vitamin D may not be sufficient for otoconia fragmentation and ultimately iBPPV, rather, chronically low vitamin D maybe required to induce otoconia degeneration.

Otopetrin-2 Immunolocalization in the Human Macula Utricle

BACKGROUND

In the present study, we investigated the localization of otopetrin-2-a member of the otopetrin family that encodes proton-selective ion channels-in the human macula utricle using immunohistochemistry.

METHODS

Macula utricle were acquired at surgery from patients who required transmastoid labyrinthectomy for intractable vertigo due to Meniere's disease (MD; n = 3) and/or vestibular drops attacks (VDA; n = 2) and from temporal bones (n = 2) acquired at autopsy from individuals with no balance disorders. Immunofluorescence staining with otopetrin-2 (rabbit affinity purified polyclonal antibody) and GFAP (mouse monoclonal antibody) to identify vestibular supporting cells was made in formalin fixed cryostat sections or whole microdissected utricle (for flat mount preparations). Secondary antibodies against rabbit and mouse were used for the identification of both proteins. Digital fluorescent images were obtained using a high-resolution laser confocal microscope.

RESULTS

Using cryostat sections and flat mount preparations otopetrin-2 immunofluorescence was seen as punctated signal throughout the supporting cells cytoplasm. GFAP immunofluorescence was present in the supporting cell cytoplasm. The distribution of otopetrin-2 was similar in the macula utricle obtained from MD, VDA, or autopsy normative patients.

CONCLUSIONS

Otopetrin-2 was localized in supporting cells in a similar fashion that otopetrin-1 previously reported in the mouse macula utricle. The differential expression of otopetrin-2 in the supporting cells of the human macula utricle suggest an important role in the vestibular sensory periphery homeostasis and otolith maintenance.

Aging and the peripheral vestibular system

Whereas much has been learned about age-related auditory changes in the inner ear, relatively little is known about the aging effects on the vestibular part of the inner ear-the peripheral vestibular system. Here we review relevant literature with regard to the prevalence of vestibular dysfunction, vestibular functional and structural changes in the elderly. The prevalence of vestibular dysfunction increases with age. Functionally, as age increases, VEMP amplitudes decrease, VEMP thresholds increase, VOR gain of HIT decreases. Due to the complexity of the vestibular system, variations in subject age and measurement techniques, findings in VEMP latency and caloric tests are conflicting. To address this, a direct measure of the peripheral vestibular system should be applied. Structurally, age-related loss in vestibular ganglion and otoconia have been noted; hair cell changes are not well defined; while subcellular changes remain to be explored. Defining how the onset of vestibular dysfunction correlates with structural degeneration will offer insights into the mechanisms underlying vestibular aging.

Benign paroxysmal positional vertigo in the elderly: current insights

Balance disorders, unsteadiness, dizziness and vertigo in the elderly are a significant health problem, needing appropriate treatment. One third of elderly patients with vertigo were diagnosed with benign paroxysmal positional vertigo (BPPV), the most common cause of dizziness in both primary care specialist Neurology and Ear Nose Throat settings. BPPV presents a specific paroxysmal positional nystagmus which can be obtained using the appropriate diagnostic positional test and can be treated effectively using specific therapeutic maneuvers. This review presents current insights into the diagnostic, pathogenetic and therapeutic aspects of BPPV in the elderly. BPPV in older patients does not differ significantly from BPPV in younger patients, with regard to pathogenesis, diagnosis and treatment. However, in older patients, its prevalence is higher and it responds less effectively to treatment, having a tendency for recurrence. Specific issues which should be considered in the elderly are: 1) difficulty in obtaining an accurate history; 2) difficulty in performing the diagnostic and therapeutic maneuvers, which should be executed with slow and gentle movements and extremely cautiously to avoid any vascular or orthopedic complications; and 3) the relation between BPPV and falls.

Magnesium as an intrinsic component of human otoconia

OBJECTIVES

To investigate morphology changes of artificial otoconia (CGC) in the presence of magnesium during growth under in vitro conditions.

METHODS

Investigating human otoconia by environmental scanning electron microscope and determining their magnesium content by energy-dispersive X-ray microanalysis (EDX). Comparing structural and morphological data of human and artificial otoconia (CGC, Ca₁Mg₀) without and with magnesium substitution (Ca_1-xMg_x).

RESULTS

EDX- and X-ray data reveals that the inorganic component in human otoconia consists of calcite containing a minor amount of magnesium substitution (Ca_1-xMg_x). CGC containing magnesium (length 397.0 ± 146.4 µm, diameter 325.6 ± 100.1 µm) are slimmer and significantly smaller (p < .01) than pure CGC (length 548.6 ± 160 µm, diameter 373.0 ± 110.4 µm) and reveal a significant influence on the final morphology. The length/diameter ratio is significantly higher by incorporation of magnesium into CGC (1.84 ± 0.25 µm versus 1.48 ± 0.11 µm in pure CGC, p < .01), which brings the overall shape to a close relationship with human otoconia (1.98 ± 0.08 µm).

CONCLUSIONS

Magnesium is an intrinsic component of human otoconia by partial substitution of calcium in the calcite crystal structure (Ca_1-xMg_x) and affects the development of the shape of artificial otoconia (calcite gelatin composites, CGC).

Age-Related Increase in Blood Levels of Otolin-1 in Humans

OBJECTIVE

To test the hypothesis that age-related demineralization of otoconia will result in an age-related increase in blood levels of otoconia matrix protein, otolin-1.

STUDY DESIGN

Cross-sectional observational clinical trial.

SETTING

Clinical research center.

PATIENTS

Seventy nine men and women ranging in age from 22 to 95 years old.

INTERVENTIONS

Diagnostic.

MAIN OUTCOME MEASURES

Blood levels of otolin-1 in relation to age.

RESULTS

Levels of otolin-1 of subjects divided into four age groups (1: 20-30 [n = 20], 2: 50-65 [n = 20], 3: 66-80 [n = 20], 4: 81-95 [n = 19] years old) demonstrated an increasing trend with age. The difference between otolin levels of groups 2 and 3, as well as, (p = 0.04) and 2 and 4 (p = 0.031) were statistically significant, but there was no significant difference between the two oldest groups.

CONCLUSIONS

Otolin-1 blood levels are significantly higher in patients older than 65 years of age. This is consistent with previous scanning electron microscopy findings of age-related otoconia degeneration and increased prevalence of benign paroxysmal positional vertigo (BPPV) with age. Normative data provided here can serve as important reference values against which levels from BPPV patients can be compared with further evaluate otolin-1 as a circulatory biomarker for otoconia degeneration.

Idiopathic benign paroxysmal positional vertigo in the elderly: a long-term follow-up study

BACKGROUND

Benign paroxysmal positional vertigo (BPPV) is the most common cause of peripheral-type vertigo in the elderly. While some studies have investigated BPPV among the elderly, no study has focused on the isolated idiopathic BPPV (iBPPV) in the elderly.

AIMS

To investigate the clinical features and recurrence rate in elderly patients diagnosed with iBPPV.

METHODS

The authors prospectively reviewed the medical records of 627 patients diagnosed with BPPV, and a total of 370 patients fulfilled the inclusion criteria. The subjects were divided into two groups by age (experimental group ≥65 years and control group 17-64 years), and the gender, numbers of canalith reposition maneuver (CRM) for successful treatment, time elapsed from onset of symptoms to clinic visit, the affected semicircular canal, and the 1- and 5-year recurrence proportion were analyzed.

RESULTS

The gender, numbers of CRM for successful treatment, affected semicircular canal, and the 1- and 5-year recurrence proportion showed no statistically significant difference between two groups (p > 0.05). The only exception was the experimental group which took a longer duration from manifestation of symptoms to hospital visit than control group (student's t test, p = 0.021).

DISCUSSION

Several previous studies report that the elderly with iBPPV shows more protracted clinical course and much higher recurrence rate than younger adult. Unlike those reports, our study showed no significant differences about the clinical features and recurrence rate between age groups.

CONCLUSION

The elderly with iBPPV could be treated as effective as general population.

[Benign paroxysmal positional vertigo: modern concepts of its etiology and pathogenesis]

The objective of the present review of the literature is the analysis of the currently available data concerning etiology and pathogenesis of benign paroxysmal positional vertigo (BPPV). The special emphasis is placed on the modern hypotheses of BPPV formation that collectively account for not more than 15% of all known cases of this condition. The best explored are the following causes of benign paroxysmal positional vertigo: vestibular neuronitis, head injuries, and disorders in the middle ear. During the recent years, much attention has been given to the role of disturbances of calcium metabolism and osteoporosis in etiology of benign paroxysmal positional vertigo. It is supposed that pathogenesis of vertiginous attacks can be explained in terms of the canalolithiasis and cupulolithiasis theories.

Clinical characteristics and treatment outcomes for benign paroxysmal positional vertigo comorbid with hypertension

CONCLUSIONS

Patients with BPPV comorbid with hypertension (h-BPPV) tend to receive a delayed diagnosis of BPPV. Comorbidity with hypertension did not influence the efficacy of the repositioning maneuver; however, comorbidity with hypertension was associated with an increased recurrence rate of BPPV.

OBJECTIVES

To determine the clinical characteristics and outcomes of h-BPPV, as well as the clinical differences between h-BPPV and idiopathic BPPV (i-BPPV).

METHODS

The authors reviewed the medical records of 41 consecutive patients with h-BPPV (the h-BPPV group) from March to December 2014 and 47 patients with i-BPPV (the i-BPPV group) during the same period.

RESULTS

There were no significant differences in age, sex ratio, or the affected side between the h-BPPV and i-BPPV groups. The proportion of patients reporting an initial episode of positional vertigo was significantly lower in the h-BPPV group (51.22% vs 74.47%; p = .024). Patients in the h-BPPV group reported a longer median episode duration than did those in the i-BPPV group (60 days vs 15 days; p = .017). The results of treatment using repositioning maneuvers were similar between the two groups. At follow-up, 13 patients in the h-BPPV group were diagnosed with recurrent BPPV compared with six in the i-BPPV group (p = .031).

The sense of balance in humans: Structural features of otoconia and their response to linear acceleration

We explored the functional role of individual otoconia within the otolith system of mammalians responsible for the detection of linear accelerations and head tilts in relation to the gravity vector. Details of the inner structure and the shape of intact human and artificial otoconia were studied using environmental scanning electron microscopy (ESEM), including decalcification by ethylenediaminetetraacetic acid (EDTA) to discriminate local calcium carbonate density. Considerable differences between the rhombohedral faces of human and artificial otoconia already indicate that the inner architecture of otoconia is not consistent with the point group -3m. This is clearly confirmed by decalcified otoconia specimen which are characterized by a non-centrosymmetric volume distribution of the compact 3+3 branches. This structural evidence for asymmetric mass distribution was further supported by light microscopy in combination with a high speed camera showing the movement of single otoconia specimen (artificial specimen) under gravitational influence within a viscous medium (artificial endolymph). Moreover, the response of otoconia to linear acceleration forces was investigated by particle dynamics simulations. Both, time-resolved microscopy and computer simulations of otoconia acceleration show that the dislocation of otoconia include significant rotational movement stemming from density asymmetry. Based on these findings, we suggest an otolith membrane expansion/stiffening mechanism for enhanced response to linear acceleration transmitted to the vestibular hair cells.

Age-Related Vestibular Loss: Current Understanding and Future Research Directions

The vestibular system sub-serves a number of reflex and perceptual functions, comprising the peripheral apparatus, the vestibular nerve, the brainstem and cerebellar processing circuits, the thalamic relays, and the vestibular cerebral cortical network. This system provides signals of self-motion, important for gaze and postural control, and signals of traveled distance, for spatial orientation, especially in the dark. Current evidence suggests that certain aspects of this multi-faceted system may deteriorate with age and sometimes with severe consequences, such as falls. Often the deterioration in vestibular functioning relates to how the signal is processed by brain circuits rather than an impairment in the sensory transduction process. We review current data concerning age-related changes in the vestibular system, and how this may be important for clinicians dealing with balance disorders.

Otoconia and otolithic membrane fragments within the posterior semicircular canal in benign paroxysmal positional vertigo

OBJECTIVES/HYPOTHESIS

Benign paroxysmal positional vertigo (BPPV) is the most common vestibular disorder with an incidence between 10.7 and 17.3 per 100,000 persons per year. The mechanism for BPPV has been postulated to involve displaced otoconia resulting in canalithiasis. Although particulate matter has been observed in the endolymph of affected patients undergoing posterior canal occlusion surgery, an otoconial origin for the disease is still questioned.

STUDY DESIGN

In this study, particulate matter was extracted from the posterior semicircular canal of two patients and examined with scanning electron microscopy.

METHODS

The samples were obtained from two patients intraoperatively during posterior semicircular canal occlusion. The particles were fixed, stored in ethanol, and chemically dehydrated. The samples were sputter coated and viewed under a scanning electron microscope. Digital images were obtained.

RESULTS

Intact and degenerating otoconia with and without linking filaments were found attached to amorphous particulate matter. Many otoconia appeared to be partially embedded in a gel matrix, presumably that which encases and anchors the otoconia within the otolith membrane, whereas others stood alone with no attached filaments and matrix. The otoconia measured roughly 2 to 8 μm in length and displayed a uniform outer shape with a cylindrical bulbous body and a 3 + 3 rhombohedral plane at each end.

CONCLUSIONS

These findings suggest that the source of the particulate matter in the semicircular canals of patients with BPPV is broken off fragments of the utricular otolithic membrane with attached and detached otoconia.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:709-714, 2017.

[Otoconia : Current aspects of research]

Otoconia are calcite-based nanocomposites containing >90 % calcite and <10 % organic material. The mean size is approximately 10 µm. The external structure of all otoconia in the utricle and saccule is similar, with a cylindrical bulbous body with a slightly hexagonal contour. The internal structure consists of a composite with varying volume thickness, dense branching structures (branches) and less dense surrounding areas (bellies). Intact otoconia can be clearly identified only by scanning electron microscopy. In the case of morphological changes (e.g. due to "degeneration") the origin of even very small particles of otoconia can be assigned using physical and chemical analytical methods. The inorganic component of otoconia (calcite) is extremely sensitive to chemical influences, which leads to morphological alterations. A "degeneration" of otoconia can be objectively accomplished in vitro by alterations in pH, electrolyte imbalance and by the influence of complex formation. These three main processes then lead to irreversible morphological alterations. Artificial (biomimetic) otoconia serve as a suitable model system for detailed investigation of growth and degenerative processes.

A Geriatric Perspective on Benign Paroxysmal Positional Vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo in older adults. Beyond the unpleasant sensation of vertigo, BPPV also negatively affects older adults' gait and balance and increases their risk of falling. As such it has a profound effect on function, independence, and quality of life. Otoconia are the inner ear structures that help detect horizontal and vertical movements. Aging contributes to the fragmentation of otoconia, whose displacement into the semicircular, most commonly posterior canals, can produce rotatory movement sensations with head movement. BPPV is more commonly idiopathic in older adults than in younger individuals, can present atypically, and has a more-protracted course and higher risk of recurrence. Medications such as meclizine that are commonly prescribed for BPPV can be associated with significant side effects. Dix-Hallpike and Head Roll tests can generally identify the involved canal. Symptoms resolve as otoconia fragments dissolve into the endolymph, but appropriate canalith repositioning (e.g., Epley maneuver) can expedite recovery and reduce the burden of this disorder. Observations suggesting an association between idiopathic BPPV and vitamin D deficiency and osteoporosis indicate that BPPV may share risk factors with other common geriatric conditions, which highlights the importance of moving beyond purely otological considerations and addressing the needs of older adults with vertigo through a systems-based multidisciplinary approach.

Persistent otolith dysfunction even after successful repositioning in benign paroxysmal positional vertigo

To evaluate utricular and saccular function during the acute and resolved phases of BPPV, ocular and cervical vestibular evoked myogenic potentials (VEMPs) were studied in 112 patients with BPPV and 50 normal controls in a referral-based University Hospital. Ocular (oVEMPs) and cervical VEMPs (cVEMPs) were induced using air-conducted sound (1000Hz tone burst, 100dB normal hearing level) at the time of initial diagnosis and 2 months after successful repositioning in patients with BPPV, and the results were compared with those of the controls. Abnormalities of cVEMPs and oVEMPs in patients with BPPV were prevalent and significantly higher compare to the healthy control group (p<0.01 in each VEMP by chi-square test). In the patient group, difference between the proportions of abnormal responses of cVEMP and oVEMP was not significant in both affected (p=0.37, chi-squared test) and non-affected (p=1.00) ears. The abnormalities were more likely reduced or absent responses rather than delayed ones; reduced or absent responses are 17.6% in cVEMPs (p=0.04, chi-square) and 21.6% in oVEMPs (p<0.01). The non-affected ear in the BPPV group also showed significantly higher abnormalities of cVEMP and oVEMP when compared to the control group. The follow-up VEMPs after repositioning maneuvers were not significantly different compared to the initial values from both stimulated affected and non-affected ears. Although most patients had unilateral BPPV, bilateral otolithic dysfunction was often shown by persistently reduced or absent cervical and ocular VEMPs, suggesting that BPPV may be caused by significant bilateral damage to the otolith organs.

Otoconia: Mimicking a calcite-based functional material of the human body. From basic research to medical aspects

Otoconia (calcite-based biominerals) are part of the sensory system in the inner ear of vertebrates, acting as gravity receptors responding to linear accelerations. Biomimetic otoconia are grown by double-diffusion into gelatine-gel matrices, and represent the first example of successful imitation of a biomineral, not only in outer shape but also in composite structure and hierarchical inner architecture. Biomimetic and biogenic (human) otoconia are investigated by X-ray methods, chemical analytics, ESEM, and TEM. Shape development (morphogenesis) as well as (partial) dissolution of the calcite component of the composite underline the hierarchical inner architecture built of more dense rhombohedral branches (with plane end-faces) and a rounded, more porous belly area. Atomistic simulations are performed in order to get insight into very first nucleation steps. Based on the detailed observations made up to now, first assumptions for the function of otoconia are developed, including the questions of density distribution within the volume of the specimen, the surrounding endolymph, as well as anchoring and interconnections of otoconia. A final point concerns the degeneration of otoconia which is caused by complexing agents and/or changes in ion concentrations (and pH) of the endolymph.

Benign Paroxysmal Positional Vertigo in the Acute Care Setting

Benign paroxysmal positional vertigo (BPPV) is a common cause of vertigo characterized by brief episodes provoked by head movements. The first attack of BPPV usually occurs in bed or upon getting up. Because it often begins abruptly, it can be alarming and lead to emergency department evaluation. The episodes of spinning often last 10 to 20 seconds, but may occasionally last as long as 1 minute. There are several forms of BPPV. In nearly all cases, highly effective treatment can be offered to patients. This article reviews the current state of our understanding of this condition and its management.

Investigating the role of Sirt1-modulated oxidative stress in relation to benign paroxysmal positional vertigo and Parkinson's disease

Benign paroxysmal positional vertigo (BPPV) is one of the most frequently encountered primary complaints in dizziness clinics. The incidence of BPPV has been proven to increase with age. The relationship between BPPV and another neurodegenerative disease, Parkinson's disease (PD), has not been previously discussed. This study aimed to investigate the relationship of BPPV and PD with oxidative stress. A total of 30,811 subjects participated in our cohort study. The study cohort comprised 5057 BPPV patients and a comparison cohort of 25,754 nonBPPV patients. SIRT1 axis gene expression was investigated in BPPV patient blood samples and a PD cell model of 6-hydroxydopamine (6-OHDA)-treated PC-12 cells to elucidate the potential in vitro and in vivo mechanisms of degeneration in PD and BPPV. Our data suggest that BPPV patients with histories of head injuries show a significantly higher hazard to develop subsequent PD (hazard ratio, 3.942; confidence interval, 1.523-10.205, p = 0.005). We also observed that oxidative status is increased in blood samples from patients with BPPV. Our in vitro study suggests that SIRT1 function is inhibited by oxidative stress, which thereby promotes 6-hydroxydopamine-induced cell death. We conclude that BPPV is independently associated with an increased risk of PD. This finding may be attributed to oxidative stress-mediated inhibition of SIRT1 expression levels.

Principles of calcite dissolution in human and artificial otoconia

Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV). The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic) otoconia (calcite gelatin nanocomposits) and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM). Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution) whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution) of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV.

Benign Paroxysmal Positional Vertigo: An Integrated Perspective

Benign paroxysmal positional vertigo (BPPV), the most common cause of dizziness, occurs in all age groups. It presents with vertigo on head movement, but in older patients presentation may be typical and thus accounting for a low recognition rate in the primary care setting. It may be recurrent in up to 50% of cases. BPPV is associated with displacement of fragments of utricular otoconia into the semicircular canals, most commonly the posterior semicircular canal. Otoconia are composed of otoconin and otolin forming the organic matrix on which calcium carbonate mineralizes. Otoconia may fragment with trauma, age, or changes in the physiology of endolymph (e.g., pH and calcium concentration). Presentation varied because otoconia fragments can be displaced into any of the semicircular canals on either (or both) side and may be free floating (canalolithiasis) or attached to the cupula (cupulolithiasis). Most cases of BPPV are idiopathic, but head trauma, otologic disorders, and systemic disease appear to be contributory in a subset. Positional maneuvers are used to diagnose and treat the majority of cases. In rare intractable cases surgical management may be considered. A strong association with osteoporosis suggests that idiopathic BPPV may have diagnostic and management implications beyond that of a purely otologic condition.