Principles of calcite dissolution in human and artificial otoconia

Acute effects of ambient air pollution on daily neurology clinic visits for vertigo: a time-series study in Wuhan, China

This study aimed to disclose the relationship between ambient air pollution and neurology clinic visits (NCVs) for vertigo. A time-series study was conducted to examine relationships between six different criteria air pollutants (SO₂, NO₂, PM_2.5, PM₁₀, CO, and O₃) and daily NCVs for vertigo in Wuhan, China, from January 1st, 2017 to November 30th, 2019. Stratified analyses were computed according to gender, age, and season. A total of 14,749 records of NCVs for vertigo were enrolled in this study. Data showed that the increase in daily NCVs for vertigo corresponding to 10 μg/m³ increase of respective pollutants are: SO₂ (- 7.60%; 95% CI: - 14.25 to - 0.44%), NO₂ (3.14%; 95% CI: 0.23 to 6.13%), PM_2.5 (0.53%; 95% CI: - 0.66 to 1.74%), PM₁₀ (1.32%; 95% CI: - 0.36 to 3.06%), CO (0.00%; 95% CI: - 0.12 to 0.13%), and O₃ (0.90%; 95% CI: - 0.01% to 1.83%). Males were more susceptible to acute exposure to SO₂ and NO₂, compared to females (SO₂: - 11.91% vs. - 4.16%; NO₂: 3.95% vs. 2.92%), whereas the acute effect of O₃ exposure was more significantly obvious in females than males (0.94% vs. 0.87%). Moreover, correlations between daily NCVs for vertigo and acute exposure to SO₂, NO₂, and O₃ were all stronger in individuals under 50 years old (SO₂: - 12.75% vs. - 4.41%; NO₂: 4.55% vs. 2.75%; O₃: 1.27% vs. 0.70%). Short-term exposure to PM_2.5 was more significantly associated with daily NCVs for vertigo in cool seasons (1.62% vs. - 0.68%), while the correlation between CO exposure and daily NCVs for vertigo was stronger in warm seasons (0.21% vs. - 0.03%). Our study demonstrated acute exposure to ambient NO₂ and O₃ positively associated with daily NCVs for vertigo. Acute effects of air pollution on daily NCVs for vertigo varied according to gender, age, and season.

Global trends in the research on benign paroxysmal positional vertigo: A 20-year bibliometric and visualization analysis

Background

Benign paroxysmal positional vertigo (BPPV) is the most common cause of peripheral vestibular vertigo. Although BPPV is benign, its underlying mechanisms are complicated, and patients diagnosed with BPPV are significantly affected by it in their daily lives. Hence, this study's purpose was to investigate global trends and frontiers in the field of BPPV.

Methods

We searched the research literature published from 2002 to 2021 on BPPV using two databases from the Web of Science Core Collection, and we conducted a bibliometric and visualization analysis. Bibliometric tools were used to perform co-authorship, co-citation, and co-occurrence analyses of countries or regions, institutions, authors, journals, keywords, and references.

Results

In all, 1,419 publications from 4,594 authors, 1,542 institutions, and 65 countries or regions with 71 subject categories were included in the study. The number of articles increased gradually from 2002 to 2021. Seoul National University, the University of Munich, and Osaka University were among the leading institutions with the most publications, while United States of America, South Korea, and China were the leading countries. JS Kim was the most prolific author, Otology & Neurotology was the most prolific journal, and Otorhinolaryngology was the most published subject category. The five most frequently occurring keywords were BPPV, vertigo, dizziness, nystagmus, and management and the top research hot spots were osteoporosis and vitamin D.

Conclusion

This study systematically analyzed trends in global scientific research on BPPV. The academic understanding of BPPV has improved significantly over the last two decades, with osteoporosis and vitamin D the two main research hot spots in the field of BPPV in recent years. These findings provide direction for current research to grasp the trends and research frontiers of current research.

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.

Serum 25-Hidroksi D Vitamini ve Kalsiyum Seviyeleri ile İdiyopatik Benign Paroksismal Pozisyonel Vertigo Arasındaki İlişki

Amaç: Kliniğimize baş dönmesi şikâyeti ile başvurup idiopathic benign paroksismal pozisyonel vertigo (BPPV) tanısı alan hastalar ile baş dönmesi olmayan sağlıklı kontrol grubunun 25-hidroksi vitamin D (25-OH vitamin D) ve Ca2+ düzeylerinin karşılaştırılması Ca2+ ve 25-OH vitamin D’nin BPPV gelişimindeki rolünün araştırılmasıdır. Gereç ve Yöntem: Çalışmamız geriye dönük vaka kontrol çalışması olup, 01.01.2018-01.08.2021 arası Alanya Egitim ve Araştırma Hastanesi Nöroloji polikliniğine başvuran İdiopatik BPPV tanısı alan 409 hasta ile kontrol grubu olarak kliniğimize başvuru öncesi son 1 yıl içerisinde vertigo, dizziness ya da dengesizlik nedeniyle hekim başvurusu olmayan serum D vitamini düzeyi ölçümü yapılmış 338 hasta seçilerek oluşturuldu. İstatiksel değerlendirmeler için ki-kare ve T testi testi kullanıldı. Bulgular: Ortalama serum 25-OH vitamin D düzeyleri BPPV ve kontrol grubunda sırasıyla 15,74 ng/mL ve 17,91 ng/mL idi. Serum 25-OH vitamin D düzeyleri BPPV grubunda kontrol grubuna göre anlamlı derecede düşük bulundu ((p=0,01, p

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.

Natural Mutations Affect Structure and Function of gC1q Domain of Otolin-1

Otolin-1 is a scaffold protein of otoliths and otoconia, calcium carbonate biominerals from the inner ear. It contains a gC1q domain responsible for trimerization and binding of Ca²⁺. Knowledge of a structure-function relationship of gC1q domain of otolin-1 is crucial for understanding the biology of balance sensing. Here, we show how natural variants alter the structure of gC1q otolin-1 and how Ca²⁺ are able to revert some effects of the mutations. We discovered that natural substitutions: R339S, R342W and R402P negatively affect the stability of apo-gC1q otolin-1, and that Q426R has a stabilizing effect. In the presence of Ca²⁺, R342W and Q426R were stabilized at higher Ca²⁺ concentrations than the wild-type form, and R402P was completely insensitive to Ca²⁺. The mutations affected the self-association of gC1q otolin-1 by inducing detrimental aggregation (R342W) or disabling the trimerization (R402P) of the protein. Our results indicate that the natural variants of gC1q otolin-1 may have a potential to cause pathological changes in otoconia and otoconial membrane, which could affect sensing of balance and increase the probability of occurrence of benign paroxysmal positional vertigo (BPPV).

Impact of air pollution on benign paroxysmal positional vertigo incidence: a retrospective study of the citizens of Seoul, South Korea

Benign paroxysmal positional vertigo (BPPV) is among the most common inner ear diseases. Although BPPV is one of the most common causes of dizziness, its pathogenesis remains unknown. Air pollutants might reach the middle ear through the eustachian tube and be absorbed into the inner ear through the round window membrane, increasing the risk of BPPV. We investigated the relationship between air pollution and BPPV risk. Data were extracted from the Korean Health Insurance Review and Assessment Service database, which contains health claims information of the entire South Korean population. Variables of interest included the number of patients diagnosed with BPPV in Seoul, South Korea, patients' clinical and demographic characteristics, and osteopenia status. Seoul's daily air pollution indicators, including SO2, CO, O3, NO2, PM10, and PM2.5, were obtained from the Korea Environment Corporation website. Overdispersed Poisson regression analysis was performed. In the multivariable analysis, NO2 air concentration (ppb) was associated with increased incidence of BPPV. In analysis stratified by gender, levels of NO2 were associated with increased incidence of BPPV in both men and women. In the analysis stratified by age, NO2 air concentration was associated with increased incidence of BPPV among all adults over the age of 19 years. In the analysis stratified by osteopenia status, NO2 was associated with increased incidence of BPPV in patients with and without osteopenia. Air levels of NO2 were associated with increased incidence of BPPV in the present study. This finding contributes toward a better understanding of BPPV pathogenesis and improved prevention and management of this condition.

Investigation of Serum Calcium and 25-Hydroxy Vitamin D Levels in Benign Paroxysmal Positional Vertigo Patients

OBJECTIVE

Benign paroxysmal positional vertigo (BPPV) is characterized by recurrent attacks of vertigo caused by head movements. It occurs as a result of otoconia falling into the semicircular canal. Calcium and 25 hydroxyvitamin D [25(OH)D] metabolism in the inner ear play an important role in otoconia formation and degeneration. Our aim in this study was to investigate the relationship between 25(OH)D levels and BPPV.

METHODS

This retrospective, case-controlled study included 52 patients with posterior canal BPPV and 52 controls aged 18 to 80 years. Age, sex, serum calcium, corrected calcium, and 25(OH)D levels of the BPPV and control group were compared.

RESULTS

Twenty-three of the patients were male (44.2%) and 29 were female (55.8%). The average age was 55.6 years. The 25(OH)D level was 15.3 ng/mL in the BPPV group and 20.2 ng/mL in controls. There was no significant difference in 25(OH)D and albumin-corrected calcium values (P = .394; P = .084, respectively). In 80.7% of the BPPV group and 61.5% of the controls, 25(OH)D levels were 20 ng/mL and below. 25 hydroxyvitamin D deficiency was found statistically significantly more frequently in patients with BPPV (P = .030).

CONCLUSION

In our study, serum 25(OH)D levels were found to be lower in patients with BPPV, and the rate of vitamin D deficiency was higher in these patients. Based on these results, it is recommended to examine the 25(OH)D levels of patients with BPPV at the time of diagnosis.

Impaired Calcium Metabolism in Benign Paroxysmal Positional Vertigo: A Topical Review

BACKGROUND AND PURPOSE

Although acute attacks of benign paroxysmal positional vertigo (BPPV) may be treated with canalith repositioning maneuvers, there have been no well-designed prospective trials to prevent this highly prevalent and recurrent disorder. This topical review explores the evidence related to the association between deficient calcium metabolism and BPPV. We also describe the development of therapeutic options to prevent recurrences of BPPV and introduce results from a recent randomized controlled trial on the effect of vitamin D and calcium supplementation in preventing BPPV recurrences.

SUMMARY OF KEY POINTS

The literature describes 3 lines of evidence on association of impaired calcium metabolism and development of BPPV: (1) decreased bone mineral density was more frequently observed in persons with BPPV than in healthy controls; (2) estrogen plays a vital role in maintenance of otoconia, and estrogen deficiency appears to precipitate degeneration of otoconia and development of BPPV; and (3) lower serum vitamin D level is associated with development of BPPV, and supplementation of vitamin D and calcium carbonate may reduce further attacks of BPPV in persons with BPPV and subnormal serum vitamin D level.

RECOMMENDATIONS FOR CLINICAL PRACTICE

Restoration of impaired calcium metabolism with supplementation of vitamin D or estrogen should be considered in the treatment of individuals with frequent recurrences of BPPV. Future randomized controlled trials are mandatory to validate these supplementation therapies in individuals with recurrent BPPV.

Causes and treatment of idiopathic benign paroxysmal positional vertigo based on endocrinological and other metabolic factors

The genesis of the Benign Paroxysmal Positional Vertigo (BPPV) seems to be related to some metabolic factors. These factors, such as vitamin D, glucocorticoids, and even thyroid and growth hormones, can affect bone metabolism and the mineralization of otoconia. It also seems to link to factors related to aging or nutritional habits. Besides, since the incidence of BPPV is quantitatively higher in women than in men, female sex steroids could be associated with this process. It could be useful to understand how these factors act in otoconial mineralization if we want to develop treatments aimed at preventing or delaying BPPV recurrences. In this review, we will analyze the role of these metabolic and hormonal factors in otoconial mineralization and in the treatment of BPPV.

[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.

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).

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.

Determinants for a Successful Sémont Maneuver: An In vitro Study with a Semicircular Canal Model

Objective

To evaluate the effect of time between the movements/steps, angle of body movements as well as the angular velocity of the maneuvers in an in vitro model of a semicircular canal (SCC) to improve the efficacy of the Sémont maneuver (SM) in benign paroxysmal positional vertigo.

Materials and Methods

Sémont maneuvers were performed on an in vitro SCC model. Otoconia trajectories were captured by a video camera. The effects of time between the movements, angles of motion (0°, 10°, 20°, and 30° below the horizontal line), different angular velocities (90, 135, 180°/s), and otoconia size (36 and 50 μm) on the final position of the otoconia in the SCC were tested.

Results

Without extension of the movements beyond the horizontal, the in vitro experiments (with particles corresponding to 50 μm diameter) did not yield successful canalith repositioning. If the movements were extended by 20° beyond the horizontal position, SM were successful with resting times of at least 16 s. For larger extension angles, the required time decreased. However, for smaller particles (36 μm), the required time doubled. The angular maneuver velocity (tested between 90 and 180°/s) did not have a major impact on the final position of the otoconia.

Interpretation

The two primary determinants for success of the SM are the time between the movements and the extension of the movements beyond the horizontal. The time between the movements should be at least 45 s. Angles of 20° or more below horizontal line (so-called Sémont+) should increase the success rate of SM.

[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.

[Current aspects of ototoxicity. Ototoxic substances and their effects]

Ototoxicity describes reversible or irreversible disorders of inner ear functions due to the influence of chemical, biological, or physical substances. Ototoxicity should be kept in mind during differential diagnosis of hearing loss, tinnitus, dizziness, and vertigo. In clinical practice, drug-induced ototoxic effects play a major role. The otorhinolaryngologist should also be involved in interdisciplinary cooperation, e.g., during treatment with antineoplastic chemotherapeutic agents with potential ototoxic side effects. In clinical practice, multimedication and interactions between different agents can complicate precise correlation in individual cases. Recent studies also show that noncellular components, such as otoconia, are extremely sensitive to chemical attacks.

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.