Immunohistochemical localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac

OBJECTIVE

This study aimed to determine the distribution and subcellular localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac.

METHODS

Ten samples of human endolymphatic sac were collected during acoustic neurinoma removal using the translabyrinthine approach. Immunohistochemistry and immunofluorescence were performed using aquaporin 2 and vasopressin type 2 receptor monoclonal antibodies.

RESULTS

Confocal microscopy demonstrated that vasopressin type 2 receptor labelling was expressed in both the apical and basolateral plasma membranes, and in the cytoplasm of the endolymphatic sac epithelium, whereas aquaporin 2 was strongly expressed at the basolateral site of the endolymphatic sac epithelium, in both the intraosseous and extraosseous parts of the endolymphatic sac.

CONCLUSION

Both aquaporin 2 and vasopressin type 2 receptor were detected in the epithelial cells of the human endolymphatic sac, suggesting that this channel may be involved in inner-ear fluid homeostasis. However, strong basolateral expression of aquaporin 2 in endolymphatic sac epithelium suggested that the function of aquaporin 2 may differ between the endolymphatic sac and kidney.

Vestibular Disorders and Hormonal Dysregulations: State of the Art and Clinical Perspectives

The interaction between endocrine and vestibular systems remains poorly documented so far, despite numerous observations in humans and animals revealing direct links between the two systems. For example, dizziness or vestibular instabilities often accompany the menstrual cycle and are highly associated with the pre-menopause period, while sex hormones, together with their specific receptors, are expressed at key places of the vestibular sensory network. Similarly, other hormones may be associated with vestibular disorders either as causal/inductive factors or as correlates of the pathology. This review was carried out according to the PRISMA method, covering the last two decades and using the MEDLINE and COCHRANE databases in order to identify studies associating the terms vestibular system and/or vestibular pathologies and hormones. Our literature search identified 646 articles, 67 of which referred directly to vestibular dysfunction associated with hormonal variations. While we noted specific hormonal profiles depending on the pathology considered, very few clinical studies attempted to establish a direct link between the expression of the vestibular syndrome and the level of circulating hormones. This review also proposes different approaches to shed new light on the link between hormones and vestibular disorders, and to improve both the diagnosis and the therapeutic management of dizzy patients.

Hormones and Vestibular Disorders: The Quest for Biomarkers

The vestibular system exerts control over various functions through neural pathways that are not yet fully mapped. Functional dysregulations or tissue lesions at different levels of the peripheral and the central vestibular networks can alter these different functions, causing a wide variety of symptoms, ranging from posturo-locomotor alterations to psychiatric syndromes such as PPPD, including the deregulation of the main biological functions. These different symptoms differ by their expression kinetics (they each appear and regress with their own kinetics) by the targets affected (muscles, organs, and brain areas) and by the sensitivity specific to each individual. Vestibular pathologies thus cover a mosaic of distinct effects, and they involve various effectors—which constitute the many markers of their different types and stages. It is therefore crucial, to predict the onset of a vertigo syndrome, to follow its temporal course, or to monitor the impact of therapeutic approaches, and to have specific and reliable biomarkers. Hormonal variations are among the possible sources of biomarkers for neurotology. We know that specific hormonal profiles can promote the appearance of vestibular disorders. We also know that the expression of vertigo syndrome is accompanied by measurable hormonal variations. The link between endocrine deregulation and vestibular alterations therefore no longer needs to be proven. However, there are still few data on their precise correlations with the vertigo syndrome. This study was undertaken with the aim to deliver an extensive review of the hormonal alterations linked to vestibular disorders. A review of the literature covering the last two decades was carried out using the MEDLINE and COCHRANE databases in order to identify studies associating the terms vestibular system or vestibular pathologies and hormones. Bibliographic data provides several outcomes in terms of therapeutic innovation in the diagnosis and therapeutic follow-up of vestibular pathologies.

Efficacy of Resection of Lateral Wall of Endolymphatic Sac for Treatment of Meniere's Disease

Background

To explore the long-term efficacy and safety of resection of the lateral wall of the endolymphatic sac for the treatment of intractable Meniere's disease (MD) as an alternative surgical procedure for treating this disorder.

Methods

Data from 73 patients who were referred to our hospital and diagnosed with unilateral MD between January 2015 and June 2019 were retrospectively analyzed in this study. Seventy-three patients who had frequent vertigo even after receiving standardized conservative treatment for at least half a year underwent resection of the lateral wall of the endolymphatic sac. Vertigo control and auditory function were assessed. Pure tone audiometry, caloric test, and vestibular evoked myogenic potential were performed to evaluate audiological and vestibular functions. The post-operative follow-up duration was more than 2 years.

Results

Among the 73 patients (male 34 cases, female 39 cases; age 20–69 years, average 51.4), vertigo was controlled effectively for 66 cases (90.4%) after 2 years of follow-up; 45 cases (61.6%) were completely controlled, and 21 cases (28.8%) were substantially controlled in this study. The patients of 16.4% had hearing loss with more than 10 dB change based on the four-tone average (0.5, 1, 2 and 3 kHz). No patient had a facial nerve weakness, cerebrospinal fluid leakage, or other complications.

Conclusion

Resection of the lateral wall of the endolymphatic sac, which can effectively control vertiginous symptoms in intractable MD patients, represents an effective and safe therapy for this disease. Resection of the lateral wall of the endolymphatic sac is expected to be used as an alternative treatment for MD.

Pathogenesis and Etiology of Ménière Disease: A Scoping Review of a Century of Evidence

Importance

Ménière disease is a rare chronic benign disorder of the inner ear with a natural history of multiple clinical phenotypes of variable severity and a tendency to burnout with time. Although multiple treatment modalities have been shown to improve the disease process-some adversely affecting cochleovestibular function-it remains uncertain whether one, several separate, or a combination of pathophysiologic mechanisms affect the disease process. A scoping review of the evidence underlying proposed pathophysiologic mechanisms of Ménière disease is needed to determine which processes are most likely to be etiopathogenic factors.

Observations

Of the 4602 relevant articles found through Embase, Ovid, and PubMed, 444 met inclusion criteria. The most common reported causes of Ménière disease were autoimmune or immune-mediated, genetic, or structural dysfunction of the inner ear. During the study period from inception to March 2021, etiologic theories shifted from structural dysfunction to autoimmune and genetic causes of Ménière disease.

Conclusions and Relevance

This scoping review found that Ménière disease is a multifactorial disease with lifelong comorbidities and loss of quality-associated life-years whose most commonly reported causes were structural dysfunction, immunologic damage, and genetic susceptibility. Recent studies have examined how autoinflammatory processes and vestibular migraine may be associated with Ménière disease. Large heterogeneity among studies may be explained by historical differences in the clinical understanding of the disease, as well as evolving intervention methodologies and practitioner expertise. Ménière disease is a multifactorial disease with lifelong comorbidities and loss of quality-associated life-years; therefore, future studies of reliable biomarkers of endolymphatic hydrops and real-time imaging are warranted to improve understanding and treatment.

Personality and psychopathology in Ménière's disease

INTRODUCTION AND OBJECTIVES

Psychological factors in vertigo patients have been extensively studied but the role of anxiety and personality traits in the clinical course of Ménière's disease (MD) is unknown. The objectives of this study are to identify and characterize psychopathology in MD and to find risk factors for an increased rate and intensity of crisis and chronic symptoms.

MATERIALS AND METHODS

We performed a transversal study in all patients diagnosed with definite MD in our department during a 5-year period. Sample subjects were interviewed in 3 steps: first, an otorhinolaryngologist collected information about clinical and pharmacological background of MD; second, a psychiatrist screened for mood, anxiety and personality disorders; in a third stage, the patient completed the DHI (Dizziness Handicap Inventory), STAI-Y (State Trait Anxiety Inventory), NEO-PI-R (Neo Personality Inventory Reviewed) and VAS (Visual Analogue Scale) for vertigo and dizziness. Statistical analysis was performed to search for risk factors for multiple and intense crisis and chronic symptoms.

RESULTS

Thirty-four patients completed all 3 phases of the study. A predominant dysfunctional personality trait was identified in 80% of patients (predominantly cluster C type), 35% were being treated with psychiatric medication and 34.4% had a considerable mood or anxiety disorder. All patients scored high (>7) in VAS during crisis. There was a statistically significant positive correlation between crisis rate and STAI, anxiety-subscale (N1) in NEO-PI-R, VAS and DHI scores (p<.044). Crises were more common in bilateral MD (p=.041). DHI scores were higher with higher STAI and N1 (p=.001). Disease duration and pure tone average were found to have a positive moderate correlation (p=.017).

CONCLUSIONS

The positive correlations between crisis rate, chronic dizziness and anxiety-related personality traits reveal a bidirectional and intimate relationship between personality, anxiety and MD, affecting these patients' quality of life. These results support the relevance of prospecting adjuvant psychological and psychiatric approaches to these patients.

Aquaporins and diseases pathogenesis: From trivial to undeniable involvements, a disease-based point of view

Aquaporins (AQPs), as transmembrane proteins, were primarily identified as water channels with the ability of regulating the transmission of water, glycerol, urea, and other small-sized molecules. The classic view of AQPs involvement in therapeutic plan restricted them and their regulators into managing only a narrow spectrum of the diseases such as diabetes insipidus and the syndrome of inappropriate ADH secretion. However, further investigations performed, especially in the third millennium, has found that their cooperation in water transmission control can be manipulated to handle other burden-imposing diseases such as cirrhosis, heart failure, Meniere's disease, cancer, bullous pemphigoid, eczema, and Sjögren's syndrome.

Identification of Potential Meniere's Disease Targets in the Adult Stria Vascularis

The stria vascularis generates the endocochlear potential and is involved in processes that underlie ionic homeostasis in the cochlear endolymph, both which play essential roles in hearing. The histological hallmark of Meniere's disease (MD) is endolymphatic hydrops, which refers to the bulging or expansion of the scala media, which is the endolymph-containing compartment of the cochlea. This histologic hallmark suggests that processes that disrupt ion homeostasis or potentially endocochlear potential may underlie MD. While treatments exist for vestibular symptoms related to MD, effective therapies for hearing fluctuation and hearing loss seen in MD remain elusive. Understanding the potential cell types involved in MD may inform the creation of disease mouse models and provide insight into underlying mechanisms and potential therapeutic targets. For these reasons, we compare published datasets related to MD in humans with our previously published adult mouse stria vascularis single-cell and single-nucleus RNA-Seq datasets to implicate potentially involved stria vascularis (SV) cell types in MD. Finally, we provide support for these implicated cell types by demonstrating co-expression of select candidate genes for MD within SV cell types.

Dynamics in Endolymphatic Hydrops & Symptoms in Meniere's Disease After Endolymphatic Duct Blockage, Preliminary Results

Objective: The purpose of the present study was to evaluate the dynamics of endolymphatic hydrops (EH) and symptoms in a group of patients who underwent endolymphatic duct blockage (EDB) for treatment of intractable Meniere's Disease (MD), and to explore a metric for verifying the effectiveness of EDB procedure.

Methods: A total of 22 patients with intractable MD patients who underwent EDB participated in the present study. EH was visualized using locally enhanced inner ear magnetic resonance imaging (MRI) prior to and following surgery. The vestibular hydrops ratio (VHR) in the second MRI examination was compared with the pre-surgery recordings.

Results: Following EDB, 6 patients exhibited complete or partial reversal of EH, complete control of vertigo spells and reported improvement in hearing; 13 patients showed no changes in EH or hearing, but 5 of these patients exhibited complete control of vertigo attacks, and the other 8 patients exhibited improved control of vertigo attacks. The final 3 patients showed an increase in EH, but symptomatic worsening in 2 patients, and symptomatic improvement in 1 patient. There was a significant difference in the average VHR prior to and following EDB. Postoperative VHR was positively correlated with the frequency of vertigo spells in the latest 6 months of follow-up and improvement of postoperative average hearing threshold.

Conclusion: The decreased EH accompanying the reduction in vertigo attacks and hearing preservation may provide a metric for verifying the effectiveness of EDB treatment in patients with MD.

Personality and psychopathology in Ménière's disease

INTRODUCTION AND OBJECTIVES

Psychological factors in vertigo patients have been extensively studied but the role of anxiety and personality traits in the clinical course of Ménière's disease (MD) is unknown. The objectives of this study are to identify and characterize psychopathology in MD and to find risk factors for an increased rate and intensity of crisis and chronic symptoms.

MATERIALS AND METHODS

We performed a transversal study in all patients diagnosed with definite MD in our department during a 5-year period. Sample subjects were interviewed in 3 steps: first, an otorhinolaryngologist collected information about clinical and pharmacological background of MD; second, a psychiatrist screened for mood, anxiety and personality disorders; in a third stage, the patient completed the DHI (Dizziness Handicap Inventory), STAI-Y (State Trait Anxiety Inventory), NEO-PI-R (Neo Personality Inventory Reviewed) and VAS (Visual Analogue Scale) for vertigo and dizziness. Statistical analysis was performed to search for risk factors for multiple and intense crisis and chronic symptoms.

RESULTS

Thirty-four patients completed all 3 phases of the study. A predominant dysfunctional personality trait was identified in 80% of patients (predominantly cluster C type), 35% were being treated with psychiatric medication and 34.4% had a considerable mood or anxiety disorder. All patients scored high (>7) in VAS during crisis. There was a statistically significant positive correlation between crisis rate and STAI, anxiety-subscale (N1) in NEO-PI-R, VAS and DHI scores (p<.044). Crises were more common in bilateral MD (p=.041). DHI scores were higher with higher STAI and N1 (p=.001). Disease duration and pure tone average were found to have a positive moderate correlation (p=.017).

CONCLUSIONS

The positive correlations between crisis rate, chronic dizziness and anxiety-related personality traits reveal a bidirectional and intimate relationship between personality, anxiety and MD, affecting these patients' quality of life. These results support the relevance of prospecting adjuvant psychological and psychiatric approaches to these patients.

MRI of endolymphatic hydrops in patients with intralabyrinthine schwannomas: a case-controlled study using non-enhanced T2-weighted images at 3 T

OBJECTIVE

Like other vestibular schwannomas developing in the internal auditory canal, intralabyrinthine schwannomas (ILS) may present with similar symptoms as in endolymphatic hydrops. Two different studies have described MR saccular hydrops in ~ 30% of internal auditory canal vestibular schwannomas, but this association has never been studied in ILS before. The aim of this work is to study the prevalence of a saccular dilation in ILS, on a T2-weigthed sequence at 3 T, compared to a control group.

MATERIAL AND METHODS

All patients presenting with typical ILS between January 2008 and October 2018 were included (n = 28, two patients with bilateral tumors) and compared to a control group (n = 53). All underwent a high-resolution T2-weighted 3D sequence (FIESTA-C). The height and width of the saccule were measured on a coronal plane by two radiologists.

RESULTS

The saccule was dilated on the side of the schwannoma in 47% of the cases (p = 0.0006 for the height, p = 0.0487 for the width). Bilateral saccular dilation was observed in 37% of the cases. There was a statistically significant correlation between the presence of a saccular hydrops and balance disorders (p = 0.02) as 50% of the patients with an intralabyrinthine schwannoma who presented with such symptoms had a saccular dilation.

CONCLUSION

Forty-seven percent of ILS are associated with homolateral saccular dilation, which is an MR sign of endolymphatic hydrops (bilateral in 37%) and it appears related to the presence of balance disorders. This opens new therapeutic potentialities with the possible use of anti-vertiginous drugs, which could have a beneficial effect on their clinical symptomatology.

MRI of endolymphatic hydrops in patients with vestibular schwannomas: a case-controlled study using non-enhanced T2-weighted images at 3 Teslas

OBJECTIVE

Vestibular schwannomas (VS) may present with similar symptoms endolymphatic hydrops. Association between hydrops and internal auditory canal VS has been described by Naganawa et al. (Neuroradiology 53:1009-1015, 2011), but has never been confirmed since. The aim of this work was to study the prevalence of a saccular dilation on a T2-weighted sequence at 3 T MRI in VS compared to a control group.

MATERIALS AND METHODS

All patients presenting with typical VS between May 2009 and July 2018 were included (n = 183) and compared to a control group (n = 53). All underwent a high-resolution T2-weighted 3D sequence (FIESTA-C). The height and width of the saccule were measured on a coronal plane by two radiologists.

RESULTS

The saccule was dilated on the side of the schwannoma in 28% of the cases (p = 2.81 × 10^- 5), with 15.7% of bilateral dilation. Saccular dilation was correlated to sensorineural hearing loss (OR 3.26, p = 0.02). There was also a significant correlation between saccular hydrops on the normal contralateral side of patients with VS and vertigo (p = 0.049), and between saccular hydrops on the side of the tumour and tinnitus (p = 0.006).

CONCLUSION

A third (29%) of VS are associated with a saccular dilation on the side of the tumour, which is an MR sign of endolymphatic hydrops (bilateral in 15.7% of the cases) and it appears related to sensorineural hearing loss and tinnitus, as well as vertigo if a contralateral dilation is present. This opens new therapeutic potentialities with the use of anti-vertiginous drugs, which could have a beneficial effect on the clinical symptoms.

Endolymphatic duct blockage for refractory Ménière's disease: assessment of intraoperative CSF leak on short-term surgical outcomes

BACKGROUND

Endolymphatic sac decompression has shown limited success for the treatment of Ménière's disease (MD). We have published a novel technique with very promising results for the treatment of refractory MD: the Endolymphatic Duct Blockage (EDB) with two titanium clips. One of the challenges of this technique was an increased incidence of intraoperative Cerebrospinal Fluid (CSF) Leak.

OBJECTIVE

To assess the effect of intraoperative CSF Leak on short-term surgical outcomes.

METHODS

Retrospective comparative study in a tertiary care center (61 patients). MD patients who underwent EDB were included. Intraoperative CSF Leaks were documented. Surgical outcomes assessed were the presence of postoperative Benign Paroxysmal Positional Vertigo (BPPV), aural fullness, tinnitus, vertigo spells and pure tone average (PTA), speech discrimination scores (SDS) and bone conduction thresholds (BCT). Data were collected for these visits: preoperative, 1 week, 1 and 6 months postoperatively.

RESULTS

Outcomes for the CSF Leak group (CSF +) (n = 22) were compared to remaining patient (CSF-) (n = 39). There was no significant difference in the occurrence of postoperative BPPV, aural fullness, tinnitus and vertigo spells. There was no significant difference in PTA, BCT or SDS between our groups at any visit.

CONCLUSIONS

Intraoperative CSF Leak may cause a temporary non-significant worsening of hearing in the first-month postoperatively without any difference at 6 months.