Assembly of the otoconia complex to the macular sensory epithelium of the vestibule

Association between vitamin D, vitamin D supplementation and benign paroxysmal positional vertigo: a systematic review and meta-analysis

Background

Benign paroxysmal positional vertigo (BPPV) is one of the most prevalent peripheral vestibular dysfunctions encountered in clinical practice, including dizziness and vertigo, which has a significant impact on people's everyday lives and affects their quality of life in many ways. Researches indicate that individuals with recurrent benign paroxysmal positional vertigo (BPPV) may exhibit vitamin D insufficiency, and certain studies suggest that correcting severe vitamin D deficiency might effectively reduce BPPV recurrence; nevertheless, the findings have been inconsistent. As a result, we conducted the current Meta-analysis to investigate potential associations of vitamin D levels with the occurrence and recurrence of BPPV. In the meantime, the current study was done to evaluate the impact of vitamin D supplementation on the prevention of benign paroxysmal positional vertigo recurrence.

Methods

Electronic databases (PubMed, EMBASE, SCOPUS and the Cochrane Library) were identified to search for relevant studies about (vitamin D or vitamin D supplementation) and (Benign paroxysmal positional vertigo incidence or recurrence) from inception to Dec 22, 2024. 60 studies with a total of 16,368 participants were included into this meta-analysis.

Results

(1) The aggregated weighted mean difference (WMD) demonstrated that there was a significant reduction in vitamin D level in the BPPV cohort (WMD = -2.84; 95% CI -4.53 to -1.15) relative to the control cohort. Likewise, Recurrent BPPV groups had significantly lower levels of vitamin D compared to non-recurrent groups (WMD = -5.01; 95% CI -6.94 to -3.08). When the cupulolithiasis BPPV groups were compared to the canalolithiasis BPPV groups, the vitamin D level was lower in the cupulolithiasis groups (WMD = 5.09; 95% CI 2.05 to 8.12); (2) In this meta-analysis, the multivariable-adjusted relative risk (RR) indicated that increased vitamin D was inversely related to BPPV incidence (RR = 1.36; 95% CI 1.31, 1.41), but not significantly related to the recurrence (RR = 0.95, 95% CI 0.91, 0.99); (3) Vitamin D supplementation group had a lower recurrence rate than the control group which did not accepted vitamin D supplementation (RR =0.45, 95% CI = 0.36-0.55).

Conclusion

The serum level of vitamin D is lower in patients with BPPV, especially recurrent BPPV, than in controls. There was a negative correlation between occurrence rate of BPPV episodes and vitamin D deficiency, which means that vitamin D deficiency may have a role in occurrence of BPPV. The present study indicates that vitamin D supplementation can significantly lower recurrence in benign paroxysmal positional vertigo. The level of vitamin D was lower in canalolithiasis than in cupulolithiasis BPPV groups.

A New Perspective to Interpret How the Vestibular Efferent System Correlates the Complexity of Routine Balance Maintenance with Management of Emergency Fall Prevention Strategies

Bipedalism is unique among mammals. Until modern times, a fall and resulting leg fracture could be fatal. Balance maintenance after a destabilizing event requires instantaneous decision making. The vestibular system plays an essential role in this process, initiating an emergency response. The afferent otolithic neural response is the first directionally oriented information to reach the cortex, and it can then be used to initiate an appropriate protective response. Some vestibular efferent axons feed directly into type I vestibular hair cells. This allows for rapid vestibular feedback via the striated organelle (STO), which has been largely ignored in most texts. We propose that this structure is essential in emergency fall prevention, and also that the system of sensory detection and resultant motor response works by having efferent movement information simultaneously transmitted to the maculae with the movement commands. This results in the otolithic membrane positioning itself precisely for the planned movement, and any error is due to an unexpected external cause. Error is fed back via the vestibular afferent system. The efferent system causes macular otolithic membrane movement through the STO, which occurs simultaneously with the initiating motor command. As a result, no vestibular afferent activity occurs unless an error must be dealt with.

Cellular and Molecular Mechanisms of Vestibular Ageing

While age-related auditory deficits and cochlear alterations are well described, those affecting the vestibular sensory organs and more broadly the central vestibular pathways are much less documented. Although there is inter-individual heterogeneity in the phenomenon of vestibular ageing, common tissue alterations, such as losses of sensory hair cells or primary and secondary neurons during the ageing process, can be noted. In this review, we document the cellular and molecular processes that occur during ageing in the peripheral and central vestibular system and relate them to the impact of age-related vestibular deficits based on current knowledge.

First paleoproteome study of fossil fish otoliths and the pristine preservation of the biomineral crystal host

Otoliths are calcium carbonate components of the stato-acoustical organ responsible for hearing and maintenance of the body balance in teleost fish. During their formation, control over, e.g., morphology and carbonate polymorph is influenced by complex insoluble collagen-like protein and soluble non-collagenous protein assemblages; many of these proteins are incorporated into their aragonite crystal structure. However, in the fossil record these proteins are considered lost through diagenetic processes, hampering studies of past biomineralization mechanisms. Here we report the presence of 11 fish-specific proteins (and several isoforms) in Miocene (ca. 14.8-14.6 Ma) phycid hake otoliths. These fossil otoliths were preserved in water-impermeable clays and exhibit microscopic and crystallographic features indistinguishable from modern representatives, consistent with an exceptionally pristine state of preservation. Indeed, these fossil otoliths retain ca. 10% of the proteins sequenced from modern counterparts, including proteins specific to inner ear development, such as otolin-1-like proteins involved in the arrangement of the otoliths into the sensory epithelium and otogelin/otogelin-like proteins that are located in the acellular membranes of the inner ear in modern fish. The specificity of these proteins excludes the possibility of external contamination. Identification of a fraction of identical proteins in modern and fossil phycid hake otoliths implies a highly conserved inner ear biomineralization process through time.

Correlation between serum vitamin D level and benign paroxysmal positional vertigo recurrence

OBJECTIVE

Benign paroxysmal positional vertigo (BPPV) is the most common cause of dizziness in the general population. BPPV is known to be closely related to the serum vitamin D level. This study aimed to examine the relationship between serum vitamin D levels and BPPV recurrence.

METHODS

A retrospective chart review was conducted on 50 patients diagnosed with posterior and lateral canal BPPV. The diagnosis of BPPV was based on the finding of vertigo and nystagmus induced by certain head positions (The Dix-Hallpike maneuver and head roll tests). The patients were classified into BPPV recurrence (Group A) and non-recurrence groups (Group B). Otolith function was assessed by cervical vestibular evoked myogenic potential (cVEMP) and ocular vestibular evoked myogenic potential (oVEMP), and their association with vitamin D levels was evaluated.

RESULTS

There were 19 subjects in Group A and 31 in Group B. There were no significant differences in age, sex, cVEMP, and oVEMP between the two groups. The average vitamin D level was 12.9 ± 8.0 ng/mL for Group A and 19.2 ± 8.2 ng/mL for Group B, and the difference between the groups was significant (p = 0.011). In the receiver operating characteristic curve analysis for BPPV recurrence with the best sensitivity and specificity, the optimal cut-off value of total serum vitamin D was determined as 12.74 ng/mL. Furthermore, reclassifying the patients based on the cut-off value showed a significantly higher recurrence rate in the group with a lower serum vitamin D level (70.5% vs. 22.5%, p = 0.007).

CONCLUSION

This complex finding highlights the importance of measuring serum vitamin D levels to monitor and evaluate patients at risk of BPPV recurrence.

Cupulolithiasis: A Critical Reappraisal

Objective

To review the history and pathophysiologic theories for cupulolithiasis and canalith jam in benign paroxysmal positional vertigo.

Data Sources

PubMed, Google Scholar.

Review Methods

Three PubMed and Google Scholar searches were performed, keywords: "cupulolithiasis," "apogeotropic [and] benign," and "canalith jam," resulting in 187 unique full-text articles in English or with English translation. Figures-Labyrinthine photographs were obtained of fresh utricles, ampullae, and cupulae of a 37-day-old mouse.

Conclusions

Freely moving otoconial masses explain most cases (>98%) of benign paroxysmal positional vertigo. Evidence that otoconia adhere strongly or persistently to the cupula is lacking. Apogeotropic nystagmus in the horizontal canal form is often attributed to cupulolithiasis; however, periampullary canalithiasis explains self-limited nystagmus, and reversible canalith jam explains prolonged apogeotropic nystagmus. Treatment-resistant cases can be explained by entrapment of particles in the canals or ampullae, but persistent adherence to the cupula remains theoretical.

Implications for Practice

Apogeotropic nystagmus is usually due to freely moving particles and should not be used in studies of horizontal canal benign paroxysmal positional vertigo as the sole method to define entrapment or cupulolithiasis. Caloric testing and imaging may help differentiate jam from cupulolithiasis. Treatment for apogeotropic benign paroxysmal positional vertigo should include maneuvers that rotate the head through 270° to fully clear the canal of mobile particles, using mastoid vibration or head shaking if entrapment is suspected. Canal plugging can be used for treatment failures.

Vitamin D Supplementation for Benign Paroxysmal Positional Vertigo: A Systematic Review

OBJECTIVE

Benign paroxysmal positional vertigo (BPPV) is commonly attributed to displaced otoconia. These have been shown to have biomineralization close to that of bone, and vitamin D deficiency has been associated with BPPV. We aim to systematically review the available literature on vitamin D supplementation and BPPV intensity and recurrence in adults.

DATABASES REVIEWED

PubMed, MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), Current Controlled Trials, and ClinicalTrials.gov.

METHODS

We systematically reviewed the available literature from 1947 to April 2020. The study protocol was registered in the PROSPERO database (trial registration: CRD42020183195).

RESULTS

A total of 179 abstracts were identified and screened by two independent reviewers. Based on inclusion and exclusion criteria, six studies were selected and subjected to a quality assessment. In one randomized clinical trial (RCT), vitamin D supplementation was found to reduce annual recurrence rate of vertigo in patient with BPPV and subnormal serum vitamin D levels compared with placebo (odds ratio, 0.69; 95% confidence interval, 0.54-0.90). Non-RCTs demonstrated the possibility of a null effect in the random effects model (odds ratio, 0.08; 95% confidence interval, 0.00-1.56). The RCT considered as low risk of bias. All of the nonrandomized studies were assessed as serious risk of bias.

CONCLUSIONS

The intervention studies identified consistently demonstrated a decrease in BPPV recurrence with supplementation of vitamin D in patients with subnormal vitamin D levels. Although there is a paucity of high-quality studies, the present literature does highlight a role for optimization of vitamin D levels in patients with BPPV.

Second harmonic generation microscopy of otoconia

The origin of second harmonic generation (SHG) signal in otoconia was investigated. SHG signal intensity from otoconia was compared to pure calcite crystals, given calcite is the primary component of otoconia and is known to emit surface SHG. The SHG intensity from calcite was found to be ∼41× weaker than the SHG intensity from otoconia signifying that the SHG signal from otoconia is likely generated from the organic matrix. Furthermore, the SHG intensity from otoconia increased when treated with a chelating agent known to dissolve calcite which confirms that calcite is not the source of SHG. Additionally, polarization-resolved SHG microscopy imaging revealed that the arrangement of the SHG emitters is radial and can form highly ordered domains.

The Relationship Between Benign Paroxysmal Positional Vertigo and Vitamin D

Introduction Benign paroxysmal positional vertigo (BPPV) is a type of vertigo and its signs are short-time, severe attacks that occur in certain head and body positions. Recent studies have revealed that vitamin D deficiency correlates with BPPV and this is explained by cupulolithiasis and canalithiasis theories. Method In the present study, levels of serum vitamin D in the patients who were diagnosed as BPPV and those in the control group consisting of healthy individuals were investigated. In addition, it was examined whether vitamin D is influential on the rates of BPPV types. In our study, 258 patients who were diagnosed with BPPV after detailed ear-nose-throat and neurology examinations were examined. We compared the control group according to their ages, genders, and levels of vitamin D. In addition, we divided the BPPV group into two sub-groups according to their vitamin D levels (20-30 ng/ml and 20 g/ml lower), and each was compared by calculating vertigo types and ratios. Results The BPPV group included 187 females and 71 males, and their mean age was 43.70 ± 15.44. The control group consisted of 65 females and 35 males, and the mean age of this group was 44.63 ± 15.42. The mean vitamin D levels of the females and males were 18.42 ± 5.07 and 19.82 ± 5.11, respectively, in this study. On the other hand, the mean vitamin D levels of healthy females and males were found to be 30.88 ± 10.74. Conclusion Our study found that the vitamin D levels of the individuals in the BPPV group were statistically significantly lower than those of the individuals who were in the control group. However, it was observed that vitamin D did not affect the rate of vertigo subtypes.

Vestibular Deficits in Deafness: Clinical Presentation, Animal Modeling, and Treatment Solutions

The inner ear is responsible for both hearing and balance. These functions are dependent on the correct functioning of mechanosensitive hair cells, which convert sound- and motion-induced stimuli into electrical signals conveyed to the brain. During evolution of the inner ear, the major changes occurred in the hearing organ, whereas the structure of the vestibular organs remained constant in all vertebrates over the same period. Vestibular deficits are highly prevalent in humans, due to multiple intersecting causes: genetics, environmental factors, ototoxic drugs, infections and aging. Studies of deafness genes associated with balance deficits and their corresponding animal models have shed light on the development and function of these two sensory systems. Bilateral vestibular deficits often impair individual postural control, gaze stabilization, locomotion and spatial orientation. The resulting dizziness, vertigo, and/or falls (frequent in elderly populations) greatly affect patient quality of life. In the absence of treatment, prosthetic devices, such as vestibular implants, providing information about the direction, amplitude and velocity of body movements, are being developed and have given promising results in animal models and humans. Novel methods and techniques have led to major progress in gene therapies targeting the inner ear (gene supplementation and gene editing), 3D inner ear organoids and reprograming protocols for generating hair cell-like cells. These rapid advances in multiscale approaches covering basic research, clinical diagnostics and therapies are fostering interdisciplinary research to develop personalized treatments for vestibular disorders.

The role of low levels of vitamin D as a co-factor in the relapse of benign paroxysmal positional vertigo (BPPV)

BACKGROUND

Benign paroxysmal positional vertigo is characterized as brief episodes of vertigo that are exacerbated by the unexpected act of moving to a current provoking location. It is thought to be an otoconia-related balance disorder. Our objectives were to assess the serum concentrations of vitamin D and calcium (total and ionized) in cases with BPPV, determine if low vitamin D levels were regarded as a cause for BPPV relapse, and determine whether vitamin D supplementation would minimize the risk of BPPV relapse.

RESULTS

Sixty cases with BPPV were included in the study; 53 cases had posterior canal BPPV, while seven had lateral canal BPPV. Canalithiasis was the most common type of BPPV pathology. Forty cases had abnormally low levels of vitamin D. There was a statistically significant positive correlation between the mean vitamin D assay for all cases with BPPV and serum calcium. There was statistically significant difference in comparing the relapse of BPPV for group that receive vitamin D after one year follow up.

CONCLUSION

Abnormal vitamin D levels were linked with the incident and relapse of BPPV. Correction of low vitamin D levels was linked with the reduction of the relapse of BPPV.

A genome-wide meta-analysis uncovers six sequence variants conferring risk of vertigo

Vertigo is the leading symptom of vestibular disorders and a major risk factor for falls. In a genome-wide association study of vertigo (Ncases = 48,072, Ncontrols = 894,541), we uncovered an association with six common sequence variants in individuals of European ancestry, including missense variants in ZNF91, OTOG, OTOGL, and TECTA, and a cis-eQTL for ARMC9. The association of variants in ZNF91, OTOGL, and OTOP1 was driven by an association with benign paroxysmal positional vertigo. Using previous reports of sequence variants associating with age-related hearing impairment and motion sickness, we found eight additional variants that associate with vertigo. Although disorders of the auditory and the vestibular system may co-occur, none of the six genome-wide significant vertigo variants were associated with hearing loss and only one was associated with age-related hearing impairment. Our results uncovered sequence variants associating with vertigo in a genome-wide association study and implicated genes with known roles in inner ear development, maintenance, and disease.

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.

Risk Factors for Recurrence of Benign Paroxysmal Positional Vertigo. A Clinical Review

Benign paroxysmal positional vertigo (BPPV) is one of the most common peripheral vestibular dysfunctions encountered in clinical practice. Although the treatment of BPPV is relatively successful, many patients develop recurrence after treatment. Our purpose is to evaluate the mean recurrence rate and risk factors of BPPV after treatment. A review of the literature on the risk factors of BPPV recurrence was performed. A thorough search was conducted using electronic databases, namely Pubmed, CINAHL, Academic Search Complete and Scopus for studies published from 2000 to 2020. Thirty studies were included in this review with 13,358 participants. The recurrence rate of BPPV ranged from 13.7% to 48% for studies with follow-up <1 year, and from 13.3% to 65% for studies with follow-up ≥2 years. Pathophysiologic mechanisms and implication of each of the following risk factors in the recurrence of BPPV were described: advanced age, female gender, Meniere’s disease, trauma, osteopenia or osteoporosis, vitamin D deficiency, diabetes mellitus, hypertension, hyperlipidemia, cardiovascular disease, migraine, bilateral/multicanal BPPV, cervical osteoarthrosis and sleep disorders. Patients with hyperlipidemia and hypertension had the highest recurrence rates of BPPV, 67.80% and 55.89%, respectively, indicating that vascular comorbidities increase the risk of BPPV recurrence. In addition, more than half of patients (53.48%) with diabetes mellitus and BPPV experienced recurrence of BPPV. Knowledge and awareness of risk factors for recurrence of BPPV are essential for the assessment and long-term prognosis of patients. Identification of these relapse risk factors may enhance the ability of clinicians to accurately counsel patients regarding BPPV and associated comorbidities.

Current and Emerging Medical Therapies for Dizziness

Medical therapies for dizziness are aimed at vertigo reduction, secondary symptom management, or the root cause of the pathologic process. Acute peripheral vertigo pharmacotherapies include antihistamines, calcium channel blockers, and benzodiazepines. Prophylactic pharmacotherapies vary between causes. For Meniere disease, betahistine and diuretics remain initial first-line oral options, whereas intratympanic steroids and intratympanic gentamicin are reserved for uncontrolled symptoms. For cerebellar dizziness and oculomotor disorders, 4-aminopyridine may provide benefit. For vestibular migraine, persistent postural perceptual dizziness and mal de débarquement, treatment options overlap and include selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants and calcium channel blockers.

Relation between vitamin D deficiency and benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common cause of positional vertigo. Vitamin D deficiency may be one of the causes of its development. To assess the relation between recurrent attacks BPPV and Vitamin D deficiency. A case control study in which 40 patients were clinically diagnosed as posterior canal BPPV, Serum 25(OH) D was measured at 1st visit. Patients were divided into two groups; group A (20 patients) received Vitamin D supplementation in addition to canal repositioning maneuver and group B (20 patients) treated by canal repositioning maneuver only. Follow up of all patients for 6 months, neuro-otological assessment was repeated and recurrent attacks were recorded. Serum vitamin D was repeated after 6 month. This study included 14 males and 26 females age ranged from 35 to 61 years, Average serum of 25 (OH) D at the first visit was (12.4 ± 2 ng/ml) for group A, and (12.2 ± 1.7 ng/ml) for group B, all patients had low serum level of 25(OH) D (below 20 ng/ml). Recurrent BPPV episodes, were significantly lower in group A than that of group B. There is a relation between BPPV recurrence and low serum Vitamin D.

CACHD1-deficient mice exhibit hearing and balance deficits associated with a disruption of calcium homeostasis in the inner ear

CACHD1 recently was shown to be an α2δ-like subunit that can modulate the activity of some types of voltage-gated calcium channels, including the low-voltage activated, T-type Ca_V3 channels. CACHD1 is widely expressed in the central nervous system but its biological functions and relationship to disease states are unknown. Here, we report that mice with deleterious Cachd1 mutations are hearing impaired and have balance defects, demonstrating that CACHD1 is functionally important in the peripheral auditory and vestibular organs of the inner ear. The vestibular dysfunction of Cachd1 mutant mice, exhibited by leaning and head tilting behaviors, is related to a deficiency of calcium carbonate crystals (otoconia) in the saccule and utricle. The auditory dysfunction, shown by ABR threshold elevations and reduced DPOAEs, is associated with reduced endocochlear potentials and increased endolymph calcium concentrations. Paint-fills of mutant inner ears from prenatal and newborn mice revealed dilation of the membranous labyrinth caused by an enlarged volume of endolymph. These pathologies all can be related to a disturbance of calcium homeostasis in the endolymph of the inner ear, presumably caused by the loss of CACHD1 regulatory effects on voltage-gated calcium channel activity. Cachd1 expression in the cochlea appears stronger in late embryonic stages than in adults, suggesting an early role in establishing endolymph calcium concentrations. Our findings provide new insights into CACHD1 function and suggest the involvement of voltage-gated calcium channels in endolymph homeostasis, essential for normal auditory and vestibular function.

Downregulation of VDR in benign paroxysmal positional vertigo patients inhibits otolith‑associated protein expression levels

Benign paroxysmal positional vertigo (BPPV) is the most common peripheral vertigo‑associated disease. Vitamin D (VD) helps maintain normal otolith function and may be associated with BPPV. VD exerts its biological functions primarily via the VD receptor (VDR). The present study demonstrated that serum VD levels were significantly decreased in patients with BPPV compared with in controls. VDR, otolith‑associated protein otoconin‑90 (OC90) and NADPH oxidase 3 (NOX3) expression levels were also significantly decreased in patients with BPPV compared with in controls. Furthermore, a positive correlation was observed between VD levels and VDR expression. Receiver operating characteristic curve analysis identified VDR expression levels as a potential diagnostic marker for BPPV. OC90 and NOX3 expression levels were notably lower in the inner ear tissue of VDR knockout mice compared with in those of wild‑type mice. In mice overexpressing VDR, OC90 and NOX3 were also overexpressed. Following intravenous injection of VD in VDR knockout mice, expression levels of OC90 and NOX3 were not significantly different from those in VDR knockout mice injected with saline. This indicated that VDR may be underexpressed in patients with BPPV and was associated with the expression levels of otolith‑associated proteins. Moreover, VDR mediated VD activation, leading to otolith protein formation. The present study provided a novel theoretical basis for BPPV onset that may facilitate the development of more effective diagnostic and treatment options.

Effect of vitamin D supplementation on benign paroxysmal positional vertigo recurrence: A meta-analysis

Benign paroxysmal positional vertigo is characterized by recurrence, which exposes patients to repeated vertigo attacks. Vitamin D deficiency has been found to be a risk factor in benign paroxysmal positional vertigo, although effect of its elimination on recurrence reduction remains unknown. To determine the effect of vitamin D supplementation in preventing recurrence of benign paroxysmal positional vertigo patients with vitamin D deficiency using a meta-analysis study. We searched and retrieved relevant articles from several databases, then used the Cochrane evaluation system or Methodological Index for Non-Randomized Studies (MINORS) to assess the quality of studies. We adopted risk-ratio (RR) with corresponding 95% confidence interval (CI) to determine effect sizes, and further performed statistical analyses under a randomized- or fixed-effects model. Seven studies, comprising 602 and 731 participants in the case and control group respectively, met our inclusion criteria, and were therefore included in the meta-analysis. Assessment based on Cochrane evaluation system or MINORS revealed that most of the studies had high quality. Moreover, the randomized- model revealed that the vitamin D supplementation group had a lower recurrence rate than the control group which did not accepted vitamin D supplementation (RR = 0.41, 95% CI = 0.26-0.65, p < 0.01). Overall, these findings indicate that vitamin D supplementation can significantly lower recurrence in benign paroxysmal positional vertigo and vitamin D deficiency.

Association Between Serum Vitamin D Level and Ménière's Disease

OBJECTIVES

Ménière's disease (MD) is a well-known inner ear disease; however, the etiopathogenesis is unknown. Several factors may be involved. Meanwhile, vitamin D is reported to have an important role in inner ear physiology. The aim of this study is to evaluate the relation between vitamin D deficiency and MD.

STUDY DESIGN

This matched case-control study compared serum vitamin D levels between patients with definite MD and those without it.

SETTING

The study was done between August 2018 and December 2019 at Ghaem University Hospital in Mashhad, Iran.

METHODS

Twenty-eight patients with definite MD were matched with a group of 84 healthy individuals, regarding age, sex, body mass index, and occupation (indoor vs outdoor). The serum level of vitamin D (25-hydroxyvitamin D3) was measured in both groups.

RESULTS

The mean ± SD vitamin D level was 18.9 ± 9.7 ng/mL in the case group and 25.2 ± 13.7 ng/mL in the control group (P = .027). There was a significant difference between the case and control groups according to the results of the conditional logistic regression model (P = .03; adjusted odds ratio, 0.96). In the MD group, 17 (60.7%) patients were vitamin D deficient, 6 (21.4%) insufficient, and only 5 (17.9%) sufficient.

CONCLUSIONS

The results of this study show that serum vitamin D level in MD is significantly lower than that of the control group. However, the role of vitamin D supplementation in the management of MD needs further study.

LEVEL OF EVIDENCE

4.

Study on embryonic and larval developmental stages of Sucker head Garra gotyla (Gray 1830; Teleostei; Cyprinidae)

Garra gotyla is an indigenous coldwater fish of the cyprinid family and has wide geographical distribution in India as well as in other countries of Asia and Africa. Induced breeding in G. gotyla was carried out successfully for the first time and an attempt has been made to document developmental stages chronologically from the first minute of fertilization, through all stages of embryonic development until the fifth day post hatching. This experiment was carried out at 22-24°C water temperature at the Directorate of Coldwater Fisheries Research, Bhimtal, India. During the breeding trial, the fertilization rate was observed as 70-75% and hatching rate was 85-90%. The mature fertilized ova were measured as 0.8-1.0 mm in diameter and the perivitelline membrane became thick soon after fertilization and formation of the germ pole. The periods taken for complete developmental stages were recorded; cleavage stage 111 min (min post fertilization (pf)), blastulation stage 580 min (pf), neurulation and segmentation 1250 min (pf) and hatching was completed after 1420 min. The sac fry was measured as 3 mm in length and took almost 3 days for complete absorption of the yolk content. The major structural and differential changes observed are in head, tail, fins, alimentary canal, rudiments of each organ and appearance of melanophore pigmentation in the whole body. The 5-day-old larvae were measured as 6 mm in length with almost every organ fully differentiated. The present study will be utilized for large-scale production of fingerlings for stock enhancement in rivers, lakes and possibilities of genetic improvement and manipulation at the embryonic stage.

Effect of Vitamin D Injection in Recurrent Benign Paroxysmal Positional Vertigo with Vitamin D Deficiency

Introduction  There have been reports indicating that patients with frequently recurring benign paroxysmal positional vertigo (BPPV) had vitamin D deficiency, and some studies indicated that the treatment of severe vitamin D deficiency is effective in the reduction of the recurrence of BPPV.

Objective  The purpose of the present study was to examine the effects of Vitamin D ₃ injection on recurrence among patients with a 10 ng/mL or lower 25-hydroxyvitamin D blood concentration diagnosed with BPPV.

Methods  Among 99 patients with idiopathic BPPV with vitamin D deficiency, 25 patients (case group) were submitted to 3 to 4 injections of 200,000 IU of vitamin D ₃ in the first year. In total, 50 patients in the control group were selected through frequency matching, with 25 patients in the case group. Age, gender, and type of BPPV are used in matching variables with 1:2 matched data. The subjects of the study group were followed up for 24 months.

Results  The differences in relapse rates between the case and the control groups were examined using the non-parametric Kruskal-Wallis test for k independent samples. With regard to the relapse rates of the entire case and control groups by period, from 0 to 6 months ( p  < 0.531), from 7 to 12 months ( p  < 1.000), and from 13 to 24 months ( p  < 0.711), and in the entire study period ( p  < 0.883) there were no statistically significant differences.

Conclusion  The present case-control study indicated that vitamin D ₃ injection had no significant effect on the recurrence of BPPV patients with vitamin D deficiency when age, gender, and type of BPPV were homogeneous between the two groups.

Review of the pathology underlying benign paroxysmal positional vertigo

The pathophysiological mechanism underlying benign paroxysmal positional vertigo (BPPV) is related to free-floating debris/otoliths in the semicircular canal (canalolithiasis) or debris/otoliths attached to the cupula (cupulolithiasis). These debris/otoliths are considered to originally accumulate after detachment from the neuroepithelium of the utricular macula secondary to a type of degeneration. An idiopathic form, which is assumed to occur spontaneously, is diagnosed when the causative pathology is obscure. However, an association between various other systemic or inner ear conditions and BPPV has been reported, indicating the existence of secondary BPPV. This study was performed to present the first review of the pathology underlying BPPV following a complete PubMed/Medline search. In total, 1932 articles published from 1975 to 2018 were reviewed. The articles were classified according to 17 potentially causative factors (aging; migraine; Meniere's disease; infection; trauma; idiopathic sudden sensorineural hearing loss; sleeping habits; osteoporosis and vitamin D insufficiency; hyperglycemia and diabetes mellitus; chronic head and neck pain; vestibule or semicircular canal pathology; pigmentation disorders; estrogen deficiency; neurological disorders; autoimmune, inflammatory, or rheumatologic disorders; familial or genetic predisposition; and allergy). A discussion of the underlying cause of BPPV for each factor is presented.

Association between serum vitamin D levels and benign paroxysmal positional vertigo: a systematic review and meta-analysis of observational studies

OBJECTIVE

Benign paroxysmal positional vertigo (BPPV) was the most common neuro-otological disorder manifests as recurrent positional vertigo, but its risk factors are elusive. Recent studies suggest that decreased Vitamin D level may be a risk factor, but the literature is inconsistent.

METHODS

The databases PubMed, Web of Science, Chinese National Knowledge Infrastructure, Wanfang, SinoMed, and Embase were systematically searched for studies on the association between BPPV and  serum Vitamin D levels published up to June 2019. Data from eligible studies were meta-analyzed using Stata 12.0.

RESULTS

A total of 18 studies were included in the analysis. Serum Vitamin D levels were significantly lower in individuals with BPPV than in controls (WMD - 2.46, 95% CI - 3.79 to - 1.12, p < 0.001). Subgroup analysis by geographical area showed that vitamin D level was significantly lower in BPPV than in controls in China (WMD - 3.27, 95% CI - 4.12 to - 2.43, p < 0.001), but not outside China (WMD - 0.90, 95% CI - 4.36 to 2.56, p = 0.611). Vitamin D levels were significantly lower in recurrent than non-recurrent BPPV across all countries in the sample (WMD 2.59, 95% CI 0.35-4.82, p = 0.023). Vitamin D deficiency emerged as an independent risk factor of BPPV (OR 1.998, 95% CI 1.400-2.851, p < 0.001).

CONCLUSION

The available evidence suggests that BPPV is associated with decreased levels of serum Vitamin D, and vitamin D deficiency was an independent risk factor for BPPV.

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.

Serum Vitamin D and Long-term Outcomes of Benign Paroxysmal Positional Vertigo

OBJECTIVES

The purpose of the present study was to examine the effect of serum vitamin D concentrations on the longterm recurrence rates of benign paroxysmal positional vertigo (BPPV) patients.

METHODS

The present study was conducted with patients diagnosed with BPPV from June 2014 to April 2016. Whether the patients' sex, age, types and locations of semicircular canals, diabetes, hypertension, hyperlipidemia, and vitamin D concentrations affect their recurrence rates was examined using Pearson chi-square tests, independent samples t-tests and Cox proportional hazards regression analyses. The effects of vitamin D concentrations on long-term recurrence rates were examined using Kaplan-Meier estimates and log-rank tests.

RESULTS

The recurrence rates obtained with Kaplan-Meier estimates were 18% and 50% at 12 months and 24 months, respectively. When the patients were divided into groups with vitamin D concentrations of <10 ng/mL and ≥10 ng/mL and the recurrence rates of the groups were compared, the difference was statistically significant (P=0.040). In addition, when the patients were divided into groups with vitamin D concentrations of <15 ng/mL and ≥15 ng/mL and the recurrence rates of the groups were compared, the difference was statistically quite significant (P=0.017). In a Cox regression model, variables such as age, sex, the types and locations of semicircular canals, hypertension, diabetes, hyperlipidemia, and 25-hydroxy vitamin D did not significantly affect recurrence.

CONCLUSION

The present study investigated the recurrence rates of BPPV in patients for a long time without limiting the sex, age, or locations of semicircular canals and it could be seen that serum vitamin D concentrations significantly affected the recurrence of BPPV.

Difference in Serum Levels of Vitamin D Between Canalolithiasis and Cupulolithiasis of the Horizontal Semicircular Canal in Benign Paroxysmal Positional Vertigo

Background and Purpose: In the horizontal canal benign paroxysmal positional vertigo (BPPV), cupulolithiasis shows apogeotropic direction changing nystagmus lasting more than 1 min, while canalolithiasis leads to geotropic direction changing nystagmus lasting < 1 min. The difference between cupulolithiasis and canalolithiasis is widely accepted to be the attachment of the displaced otoconia to the cupula of a semicircular canal. Several studies have shown a relationship between BPPV and vitamin D deficiency, but no studies have compared serum levels of vitamin D between canalolithiasis and cupulolithiasis patients. The purpose of this study was to clarify the difference in vitamin D serum level between canalolithiasis and cupulolithiasis of the horizontal canal.

Methods: This retrospective study included 20 and 15 patients with canalolithiasis and cupulolithiasis of the horizontal canal, respectively. Serum levels of 25-hydroxyvitamin D [25(OH)D] during the acute phase of BPPV were measured.

Results: The mean 25(OH)D serum level in patients with canalolithiasis and cupulolithiasis was 13.2 ± 1.4 and 20.4 ± 1.6 ng/mL, respectively, and the difference was statistically significant (p = 0.0014), also after adjusting for age and sex (p = 0.0351). Eighteen out of 20 (90%) and 5 of 15 (33%) patients were diagnosed with vitamin D deficiency in the canalolithiasis and cupulolithiasis groups, respectively, and this difference was also statistically significant (p = 0.0005).

Conclusion: We found that serum vitamin D level in patients with canalolithiasis was significantly lower than that in patients with cupulolithiasis of the horizontal canal.

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.

Ectopic otoconial formation in the lagena of the pigeon inner ear

The vertebrate inner ear contains vestibular receptors with dense crystals of calcium carbonate, the otoconia. The production and maintenance of otoconia is a delicate process, the perturbation of which can lead to severe vestibular dysfunction in humans. The details of these processes are not well understood. Here, we report the discovery of a new otoconial mass in the lagena of adult pigeons that was present in more than 70% of birds. Based on histological, tomographic and elemental analyses, we conclude that the structure likely represents an ectopically-formed otoconial assembly. Given its frequent natural occurrence, we suggest that the pigeon lagena is a valuable model system for investigating misregulated otoconial formation.This article has an associated First Person interview with the first author of the paper.

Osteoporosis is associated with increased risk for benign paroxysmal positional vertigo: a nationwide population-based study

Recent evidence has indicated that osteoporosis is a risk factor for benign paroxysmal positional vertigo (BPPV). This large population-based study demonstrated that patients with osteoporosis had a 1.82-fold higher risk of developing BPPV than those without osteoporosis through the use of the Taiwan National Health Insurance Research Database.

PURPOSE

Benign paroxysmal positional vertigo (BPPV) is one of the most frequent causes of vertigo. Osteoporosis reflects a homeostatic imbalance in the rate of bone turnover, with the rate of bone resorption exceeding that of bone formation. Recent evidence has indicated that osteoporosis is a risk factor for BPPV. We aimed to validate the risk of BPPV in osteoporotic patients through a nationwide, population-based, cohort study.

METHODS

Patients treated for osteoporosis were identified from entries made in the Taiwan National Health Insurance Research Database (NHIRD) between 2000 and 2013. Each osteoporosis patient was age- and sex-matched with four randomly selected subjects without osteoporosis. We compared the incidence rates of BPPV in the two cohorts (with and without osteoporosis) and identified risk factors.

RESULTS

We identified 6649 osteoporosis patients and 26,596 match controls. According to the incidence of BPPV among the two groups, patients with osteoporosis were found to have a 1.82-fold higher risk of developing BPPV than those without osteoporosis. The incidence rate ratio (IRR) between osteoporotic patients and the control cohort was 2.0 (p < 0.001).

CONCLUSIONS

This large population-based study demonstrated that patients with osteoporosis were associated with an increased risk for BPPV. The results of this study provide some insight into the management of BPPV.

Estradiol deficiency is a risk factor for idiopathic benign paroxysmal positional vertigo in postmenopausal female patients

OBJECTIVES/HYPOTHESIS

Although it is generally considered that benign paroxysmal positional vertigo (BPPV) is associated with changes in female sex hormone levels, no direct data have been reported until now. The purpose of this article was to provide direct data showing the distinct relationship between female sex hormone fluctuations and BPPV in postmenopausal female patients.

STUDY DESIGN

Prospective analysis in humans and basic research in animals.

METHODS

Blood samples were analyzed to determine the levels of estradiol, progesterone, follicle-stimulating hormone, and luteinizing hormone in 50- to 80-year-old postmenopausal female patients newly diagnosed with idiopathic BPPV based on history compatible with BPPV and positive provocative maneuvers. Animal models of bilateral ovariectomy and female sex hormone replacement therapy were used to further confirm the relationship between BPPV and female sex hormone levels by determining the expression levels of otoconin 90, the protein suggested as essential in the dislocation of otoconia.

RESULTS

Statistically significant differences between the estradiol level of BPPV patients and the control group were found (P < .001). Moreover, in bilateral ovariectomy in rats, 17β-estradiol replacement reversed the decrease of otoconin 90 levels.

CONCLUSIONS

Our results suggest that estradiol deficiency may be an important risk factor for idiopathic benign paroxysmal positional vertigo in postmenopausal female patients.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:948-953, 2018.

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.

Formation of the inner ear during embryonic and larval development of the cichlid fish (Oreochromis mossambicus)

BACKGROUND

The vertebrate inner ear comprises mineralized elements, namely the otoliths (fishes) or the otoconia (mammals). These elements serve vestibular and auditory functions. The formation of otoconia and otoliths is described as a stepwise process, and in fish, it is generally divided into an aggregation of the otolith primordia from precursor particles and then a growth process that continues throughout life.

RESULTS

This study was undertaken to investigate the complex transition between these two steps. Therefore, we investigated the developmental profiles of several inner ear structural and calcium-binding proteins during the complete embryonic and larval development of the cichlid fish Oreochromis mossambicus in parallel with the morphology of inner ear and especially otoliths. We show that the formation of otoliths is a highly regulated temporal and spatial process which takes place throughout embryonic and larval development.

CONCLUSIONS

Based on our data we defined eight phases of otolith differentiation from the primordia to the mature otolith.

Risk Assessment of Neonatal Exposure to Low Frequency Noise Based on Balance in Mice

General electric devices and ventilation systems are known to generate low frequency noise (LFN) with frequencies of <100 Hz. Previous studies showed that exposure to LFN caused impairments of balance in humans and mice during adulthood. On the other hand, a previous study showed that noise levels in the neonatal intensive care unit (NICU) were greater than those in general home or office environments. Therefore, it is possible that neonates have a potential risk to be exposed to LFN in the NICU. However, the risk of neonatal exposure to LFN remains unclear in humans and mice. In this study, male ICR mice were exposed to LFN at 100 Hz for 4 weeks after birth and then subjected to rotarod and beam crossing tests in order to assess LFN-mediated risk of imbalance during the neonatal period. Exposure to LFN at 70 dB, but not exposure to LFN up to 60 dB, during the neonatal period significantly decreased performance scores for rotarod and beam crossing tests compared to the scores of the control group. The number of calbindin-positive hair cells in the saccule and utricle was decreased in mice exposed to LFN at 70 dB for 4 weeks in the neonatal phase. Cessation of exposure for 10 weeks did not result in recovery of the decreased performance in rotarod and beam crossing tests. Thus, our results suggest that 70 dB is a possible threshold for exposure to LFN for 4 weeks during the neonatal period causing unrecoverable imbalance in mice.

Development of a murine model of traumatic benign paroxysmal positional vertigo: a preliminary study

CONCLUSION

The results showed a gradual detachment of otoconia in the utricle after a single event of head vibration, possibly explaining the frequent recurrence of BPPV attacks and persistent dizziness after trauma.

OBJECTIVES

This study developed a murine model of traumatic BPPV and observed the changes in otoconia detachment over time.

METHODS

Six-week-old CBA mice were used in this study. Otoconia detachment was induced by vibrating the head for 2 min. Utricles of mice were harvested from different groups: before the head vibration and 1 day, 1 week, 1 month, and 3 months after vibration application. Using scanning electron microscopy and ImageJ software, the percentage of the intact area of otoconia in the utricle was calculated. Hearing thresholds were compared among the groups.

RESULTS

The mean (± SD) percentages of the intact area of otoconia in the utricle were 98.1% ± 1.7% before the vibration and 93.6% ± 1.7%, 88.9% ± 5.3%, 78.2% ± 20.9%, and 38.9% ± 24.1% at 1 day, 1 week, 1 month, and 3 months after the vibration, respectively. The percentage decreased significantly over time after the vibration (p < .001). The hearing thresholds were not different among the groups.

Spatiotemporal differences in otoconial gene expression

Otoconia are minute biocrystals composed of glycoproteins, proteoglycans, and CaCO₃ , and are indispensable for sensory processing in the utricle and saccule. Otoconia abnormalities and degeneration can cause or facilitate crystal dislocation to the ampulla, leading to vertigo and imbalance in humans. In order to better understand the molecular mechanism controlling otoconia formation and maintenance, we have examined the spatial and temporal expression differences of otoconial genes in the mouse inner ear at developmental, mature and aging stages using whole transcriptome sequencing (RNA-Seq) and quantitative RT-PCR. We show that the expression levels of most otoconial genes are much higher in the utricle and saccule compared with other inner ear tissues before postnatal stages in C57Bl/6J mice, and the expression of a few of these genes is restricted to the embryonic utricle and saccule. After the early postnatal stages, expression of all otoconial genes in the utricle and saccule is drastically reduced, while a few genes gain expression dominance in the aging ampulla, indicating a potential for ectopic debris formation in the latter tissue at old ages. The data suggest that the expression of otoconial genes is tightly regulated spatially and temporally during developmental stages and can become unregulated at aging stages. Birth Defects Research (Part A) 106:613-625, 2016. © 2016 Wiley Periodicals, Inc.

Serum vitamin D and recurrent benign paroxysmal positional vertigo

Objectives

The objective of the present study was to examine the effects of serum 25‐hydroxyvitamin D concentrations on patients diagnosed with benign paroxysmal positional vertigo (BPPV) on BPPV recurrence.

Study Design

Case series.

Methods

A retrospective review of 232 patients diagnosed with BPPV visiting the clinic between June 2014 and June 2015 was performed. All patients underwent a complete otolaryngological, audiologic, and neurologic evaluation. The appropriate particle‐repositioning maneuver was performed depending on the type of BPPV. The patients were divided into the recurrence group and the nonrecurrence group. Age, gender, follow‐up period, type of BPPV, and vitamin D concentrations in the two groups were compared and analyzed through binary logistic regression analyses.

Results

The average follow‐up period after treatment was 10.2 months. Forty‐one (17.7%) of 232 patients suffered a recurrence during the follow‐up period. The mean vitamin D concentration of 191 patients who did not suffer any recurrence was 16.63 ng/mL, whereas that of 41 patients who suffered a recurrence was 13.64 ng/mL. This difference in vitamin D concentrations was statistically significant (P < 0.019). The patients' age, gender, follow‐up period, and type of BPPV had no statistically significant impact.

Conclusion

Vitamin D is assumed to affect BPPV as a recurrence factor independent of age, gender, follow‐up period, and type of BPPV.

Level of Evidence

4.

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.

Molecular aging of the mammalian vestibular system

Dizziness and imbalance frequently affect the elderly and contribute to falls and frailty. In many geriatric patients, clinical testing uncovers a dysfunction of the vestibular system, but no specific etiology can be identified. Neuropathological studies have demonstrated age-related degeneration of peripheral and central vestibular neurons, but the molecular mechanisms are poorly understood. In contrast, recent studies into age-related hearing loss strongly implicate mitochondrial dysfunction, oxidative stress and apoptotic cell death of cochlear hair cells. While some data suggest that analogous biological pathomechanisms may underlie vestibular dysfunction, actual proof is missing. In this review, we summarize the available data on the molecular causes of vestibular dysfunction.

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.

Otolith tethering in the zebrafish otic vesicle requires Otogelin and α-Tectorin

Otoliths are biomineralised structures important for balance and hearing in fish. Their counterparts in the mammalian inner ear, otoconia, have a primarily vestibular function. Otoliths and otoconia form over sensory maculae and are attached to the otolithic membrane, a gelatinous extracellular matrix that provides a physical coupling between the otolith and the underlying sensory epithelium. In this study, we have identified two proteins required for otolith tethering in the zebrafish ear, and propose that there are at least two stages to this process: seeding and maintenance. The initial seeding step, in which otolith precursor particles tether directly to the tips of hair cell kinocilia, fails to occur in the einstein (eis) mutant. The gene disrupted in eis is otogelin (otog); mutations in the human OTOG gene have recently been identified as causative for deafness and vestibular dysfunction (DFNB18B). At later larval stages, maintenance of otolith tethering to the saccular macula is dependent on tectorin alpha (tecta) function, which is disrupted in the rolling stones (rst) mutant. α-Tectorin (Tecta) is a major constituent of the tectorial membrane in the mammalian cochlea. Mutations in the human TECTA gene can cause either dominant (DFNA8/12) or recessive (DFNB21) forms of deafness. Our findings indicate that the composition of extracellular otic membranes is highly conserved between mammals and fish, reinforcing the view that the zebrafish is an excellent model system for the study of deafness and vestibular disease.

The zebrafish merovingian mutant reveals a role for pH regulation in hair cell toxicity and function

Control of the extracellular environment of inner ear hair cells by ionic transporters is crucial for hair cell function. In addition to inner ear hair cells, aquatic vertebrates have hair cells on the surface of their body in the lateral line system. The ionic environment of these cells also appears to be regulated, although the mechanisms of this regulation are less understood than those of the mammalian inner ear. We identified the merovingian mutant through genetic screening in zebrafish for genes involved in drug-induced hair cell death. Mutants show complete resistance to neomycin-induced hair cell death and partial resistance to cisplatin-induced hair cell death. This resistance is probably due to impaired drug uptake as a result of reduced mechanotransduction ability, suggesting that the mutants have defects in hair cell function independent of drug treatment. Through genetic mapping we found that merovingian mutants contain a mutation in the transcription factor gcm2. This gene is important for the production of ionocytes, which are cells crucial for whole body pH regulation in fish. We found that merovingian mutants showed an acidified extracellular environment in the vicinity of both inner ear and lateral line hair cells. We believe that this acidified extracellular environment is responsible for the defects seen in hair cells of merovingian mutants, and that these mutants would serve as a valuable model for further study of the role of pH in hair cell function.

Benign paroxysmal positional vertigo--toward new definitions

OBJECTIVE

To review new clinical data and theories concerning atypical positional nystagmus in vertical canal benign paroxysmal positional vertigo (BPPV).

DATA SOURCES

Peer reviewed, clinical papers describing nystagmus provoked by positioning in cases with BPPV.

STUDY SELECTION

Basic scientific articles detailing 3D anatomical reconstructions of the inner ear.

CONCLUSION

In BPPV, it is hypothetically possible that otoconia become dislocated but do not fall into the common crus of the vertical canals or into the horizontal canal; in these cases, they may gravitate toward the most inferior part of the utriculus, the ampulla of the inferior canal. It is argued that in these cases, depending on their behavior (free-floating or sticking to the cupula) and the precise position of the inferior ampulla, either no nystagmus or a slow downbeat nystagmus should ensue when the patient is positioned from sitting to a Dix-Hallpike position. Such scenarios could hypothetically explain commonly seen clinical entities such as "subjective BPPV" and/or cases with a peripheral positional downbeat nystagmus.

The role of ear stone size in hair cell acoustic sensory transduction

Hearing and bodily balance are different sensations initiated by a common mechanism. Both sound- and head movement-dependent mechanical displacement are converted into electrical signals by the sensory hair cells. The saccule and utricle inner ear organs, in combination with their central projections to the hindbrain, are considered essential in fish for separating auditory and vestibular stimuli. Here, we established an in vivo method in larval zebrafish to manipulate otolith growth. We found that the saccule containing a large otolith is necessary to detect sound, whereas the utricle containing a small otolith is not sufficient. Otolith removal and relocation altered otolith growth such that utricles with experimentally enlarged otoliths acquired the sense of sound. These results show that otolith biomineralization occurs in a region-specific manner, and suggest that regulation of otolith size in the larval zebrafish ear is crucial to differentially sense auditory and vestibular information.

Otolithic membrane damage in patients with endolymphatic hydrops and drop attacks

OBJECTIVES

1. Evaluate the otolithic membrane in patients with endolymphatic hydrops (EH) and vestibular drop attacks (VDA) undergoing ablative labyrinthectomy. 2. Correlate intraoperative findings to archival temporal bone specimens of patients with EH.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center. SPECIMEN SOURCE: 1. Patients undergoing labyrinthectomy for incapacitating Ménière's disease (MD), delayed EH, VDA, or acoustic neuroma (AN) between 2004 and 2011. 2. Archival temporal bone specimens of patients with MD.

INTERVENTIONS

Ablative labyrinthectomy.

MAIN OUTCOME MEASURES

Examination of the utricular otolithic membrane.

RESULTS

The otolithic membrane of the utricle was evaluated intraoperatively in 28 patients undergoing labyrinthectomy. Seven (25%) had a history of VDA, 6 (21%) had delayed EH, 9 (32%) had MD, and 6 (21%) had AN. All patients with VDA showed evidence of a disrupted utricular otolithic membrane, whereas only 50% and 56% of patients with delayed EH and MD, respectively, demonstrated otolithic membrane disruption (p = 0.051). None of the patients with AN showed otolithic membrane disruption (p = 0.004). The mean thickness of the otolithic membrane in 5 archival temporal bone MD specimens was 11.45 micrometers versus 38 micrometers in normal specimens (p = 0.001).

CONCLUSION

The otolithic membrane is consistently damaged in patients with VDA. In addition, there is a significantly higher incidence of otolithic membrane injury in patients with MD and delayed EH compared with patients without hydrops, suggesting that the underlying pathophysiology in VDA results from injury to the otolithic membrane of the saccule and utricle, resulting in free-floating otoliths and atrophy.

Retinoic acid deficiency impairs the vestibular function

The retinaldehyde dehydrogenase 3 (Raldh3) gene encodes a major retinoic acid synthesizing enzyme and is highly expressed in the inner ear during embryogenesis. We found that mice deficient in Raldh3 bear severe impairment in vestibular functions. These mutant mice exhibited spontaneous circling/tilted behaviors and performed poorly in several vestibular-motor function tests. In addition, video-oculography revealed a complete loss of the maculo-ocular reflex and a significant reduction in the horizontal angular vestibulo-ocular reflex, indicating that detection of both linear acceleration and angular rotation were compromised in the mutants. Consistent with these behavioral and functional deficiencies, morphological anomalies, characterized by a smaller vestibular organ with thinner semicircular canals and a significant reduction in the number of otoconia in the saccule and the utricle, were consistently observed in the Raldh3 mutants. The loss of otoconia in the mutants may be attributed, at least in part, to significantly reduced expression of Otop1, which encodes a protein known to be involved in calcium regulation in the otolithic organs. Our data thus reveal a previously unrecognized role of Raldh3 in structural and functional development of the vestibular end organs.