Detection of viral DNA in the endolymphatic sac in Ménière's disease by in situ hybridization

Meniere's Disease Patients with Distinct Sac Pathoanatomic Findings React Differently to Endolymphatic Duct Blockage

OBJECTIVES

To explore the possible difference in response to endolymphatic duct blockage (EDB) treatment in patients with Meniere's disease (MD) with distinct pathoanatomic characteristics of the sac.

METHODS

In a total of 24 patients with MD receiving EDB treatment, the dynamics of the vertigo attack, hearing, vestibular function, and endolymph hydrops (EH) before surgery and 40 months following surgery in patients with normoplastic extraosseous portion of endolymphatic sac (eES) were compared with that in patients with atrophic eES.

RESULTS

A higher prevalence of complete vertigo control, better cochlear and vestibular function, and lower endolymph to vestibule-volume ratio were found in patients with normoplastic eES than in those with atrophic eES. Moreover, the reversal of EH was found in a total of six patients in normoplastic eES group, but no reversal of EH was detected in the atrophic eES group after surgery.

CONCLUSIONS

A difference in response to EDB treatment was shown in the MD patients with normoplastic eES and those with atrophic eES; the reversal of EH was found in the normoplastic eES group, but not in the atrophic eES group after surgery, suggesting two distinct pathologies in the eESs may underlie the pathogenesis of EH in two subgroups of MD patients.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:2761-2769, 2023.

Infectious causes and mimickers of meniere's disease

PURPOSE OF REVIEW

To review the evidence of a possible viral etiology of Meniere's disease, the role of antiviral therapy, as well as other infectious disease processes that may mimic Meniere's disease. Better understanding of the etiology of Meniere's disease and the role of various infectious disease processes may allow for more effective diagnosis and management.

RECENT FINDINGS

There is evidence that viral infections - to Herpes simplex virus, cytomegalovirus, Epstein Barr virus, influenza, adenovirus, Coxsackie virus B, and Varicella Zoster Virus - may be involved in the development of Meniere's disease, however the evidence is inconsistent and the underlying mechanism remains theoretical. Nevertheless, antiviral therapy may be effective for a subset of patients with Meniere's disease. Lastly, other infectious diseases including Lyme disease and syphilis can present with symptoms similar to Meniere's disease. It is important to discern these from Meniere's disease to determine the appropriate treatment.

SUMMARY

There is a paucity of high-quality evidence to support a viral etiology of Meniere's disease, and the current evidence appears circumstantial and inconsistent. Additional research is necessary to establish the mechanism and causative pathogens. Antiviral therapy may provide therapeutic benefit for a subset of patients with Meniere's disease. Furthermore, clinicians should be aware of other infectious mimics of Meniere's disease and include them in the differential diagnosis of patients presenting with Meniere's-like symptoms. Research on this subject continues to evolve, and data from these studies represent a growing repository of evidence that can be used to guide clinical decision-making.

Up-Regulated Expression of Interferon-Gamma, Interleukin-6 and Tumor Necrosis Factor-Alpha in the Endolymphatic Sac of Meniere's Disease Suggesting the Local Inflammatory Response Underlies the Mechanism of This Disease

Background

Immune mediated inflammatory changes affecting the endolymphatic sac (ES) may underlie the pathology of Meniere's disease (MD). The aim of the present study was to explore the differentially expressed cytokines in ES luminal fluid (ELF) of patients with MD, and the correlation between the expression of cytokines in the ELF with that in the serum was determined by quantitatively analyzing the cytokines in human ELF and serum.

Methods

Human ELF, serum and ES tissues were collected from patients with unilateral MD and patients with acoustic neuroma (AN) during surgery. The Simoa Cytokine 6-Plex Panel kit was used to analyze the levels of cytokines in the ELF and blood samples of the patients. Immunohistochemistry and immunofluorescence were subsequently used to validate the relative expression levels of the cytokines in MD.

Results

Significant differences were identified in the expression levels of interferon-γ (IFN-γ) (P < 0.001), interleukin (IL)-6 (P = 0.008) and tumor necrosis factor-α (TNF-α) (P = 0.036) in the luminal fluid of the ES comparing between the MD and AN groups. By contrast, the levels of IFN-γ, IL-10, IL-12p70, IL-17A, IL-6 and TNF-α in the serum of the MD group were not significantly different from those of either the AN group or healthy control subjects. In addition, no significant correlations in the expression levels of cytokines compared between the ELF and serum were found for the patients in either the MD or the AN group. Finally, the detection of positive expression of TNF-α, IL-6 and IFN-γ in the epithelial cells of the majority of ES specimens from patients with MD confirmed the up-regulated expression of these cytokines in the ES of patients with MD.

Conclusions

The identification of up-regulated expression levels of TNF-α, IL-6 and IFN-γ in the ELF in the present study has provided direct evidence for an increased immunologic activity in the microenvironment of the ES in patients with unilateral MD, may suggest the local inflammatory response underlies the mechanism of this disease.

Are viral-infections associated with Ménière's Disease? A systematic review and meta-analysis of molecular-markers of viral-infection in case-controlled observational studies of MD

Despite considerable research, it remains controversial as to whether viral-infections are associated with Meniere’s Disease (MD), a clinically heterogeneous set of chronic inner-ear disorders strongly associated with endolymphatic hydrops. Here, we investigated whether viral-infections are associated with MD through a systematic review and meta-analysis of observational clinical studies using molecular-diagnostics. Eligible for inclusion were case-controlled studies which ascertained molecular-determinants of past or present viral-infection through either viral nucleic acids or host serological marker in MD cases and non-MD controls. Across online databases and grey literature, we identified 210 potentially relevant articles in the English language, from which a total of 14 articles fully satisfied our eligibility criteria such that meta-groups of 611 MD-cases and 373 controls resulted. The aggregate quality of the modest-sized (14 studies) body of evidence was limited and varied considerably with regards to participant selection, matching, and ascertainment(s) and determinant(s) of viral-infection. Most data identified concerned the human cytomegalovirus (CMV), and meta-analysis of eligible studies revealed that evidence of CMV-infection was associated approximately three-fold with MD compared to controls, however the timing of the infections was indeterminate as the pooled analyses combined antiviral serological markers with viral nucleic acid markers. No association was found for any of HSV-1, -2, VZV, or EBV. Associative analyses of any viral species not aforementioned were precluded by limited data, and thus potential associations between other viral species and MD, especially other than Herpesviridae, are yet to be characterised. Overall, we have found a small association between CMV-infection and MD, however it is to be determined for what sub-groups of MD this finding may be relevant, and ideally the reported association remains would be reproduced by a greater volume of higher quality evidence.

Pathophysiologic Findings in the Human Endolymphatic Sac in Endolymphatic Hydrops: Functional and Molecular Evidence

BACKGROUND

The endolymphatic sac (ES) is a cystic structure situated on the posterior fossa dura and is connected to the luminal space of the vestibular organ through the endolymphatic duct, which branches into the utricular and saccular ducts. Unlike the cochlea and vestibule, the ES does not contain sensory epithelium in its luminal space, and a single layer of epithelial cells line the luminal surface area. The ES in the inner ear is thought to play a role in the regulation of inner ear homeostasis, fluid volume, and immune reaction. If these functions of the ES are disrupted, dysfunction of the inner ear may develop. The most well-known pathology arising from dysfunction of the ES is endolymphatic hydrops, characterized by an enlarged endolymphatic space due to the accumulation of excessive endolymphatic fluid. Although, molecular identities and functional evidence for the roles were identified in animal studies, basic studies of the human ES are relatively uncommon compared with those using animal tissues, because of limited opportunity to harvest the human ES.

METHODS

In this study, molecular and functional evidence for the role of the human ES in the development of endolymphatic hydrops are reviewed.

RESULTS AND CONCLUSIONS

Although evidence is insufficient, studies using the human ES have mostly produced findings similar to those of animal studies. This review may provide a basis for planning further studies to investigate the pathophysiology of disorders with the finding of endolymphatic hydrops.

Looking back to move forward: a twenty-year audit of herpes zoster in Asia-Pacific

Background

Herpes zoster (HZ) is a prevalent viral disease that inflicts substantial morbidity and associated healthcare and socioeconomic burdens. Current treatments are not fully effective, especially among the most vulnerable patients. Although widely recommended, vaccination against HZ is not routine; barriers in Asia-Pacific include long-standing neglect of adult immunisation and sparse local data. To address knowledge gaps, raise awareness, and disseminate best practice, we reviewed recent data and guidelines on HZ from the Asia-Pacific region.

Methods

We searched PubMed, Scopus, and World Health Organization databases for articles about HZ published from 1994 to 2014 by authors from Australia, China, Hong Kong, India, Indonesia, Japan, Korea, Malaysia, New Zealand, the Philippines, Singapore, Taiwan, Thailand, and Vietnam. We selected articles about epidemiology, burden, complications, comorbidities, management, prevention, and recommendations/guidelines. Internet searches retrieved additional HZ immunisation guidelines.

Results

From 4007 retrieved articles, we screened-out 1501 duplicates and excluded 1264 extraneous articles, leaving 1242 unique articles. We found guidelines on adult immunisation from Australia, India, Indonesia, Malaysia, New Zealand, the Philippines, South Korea, and Thailand.

HZ epidemiology in Asia-Pacific is similar to elsewhere; incidence rises with age and peaks at around 70 years – lifetime risk is approximately one-third. Average incidence of 3–10/1000 person-years is rising at around 5% per year. The principal risk factors are immunosenescence and immunosuppression. HZ almost always causes pain, and post-herpetic neuralgia is its most common complication. Half or more of hospitalised HZ patients have post-herpetic neuralgia, secondary infections, or inflammatory sequelae that are occasionally fatal. These disease burdens severely diminish patients’ quality of life and incur heavy healthcare utilisation.

Conclusions

Several countries have abundant data on HZ, but others, especially in South-East Asia, very few. However, Asia-Pacific countries generally lack data on HZ vaccine safety, efficacy and cost-effectiveness. Physicians treating HZ and its complications in Asia-Pacific face familiar challenges but, with a vast aged population, Asia bears a unique and growing burden of disease. Given the strong rationale for prevention, most adult immunisation guidelines include HZ vaccine, yet it remains underused. We urge all stakeholders to give higher priority to adult immunisation in general and HZ in particular.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2198-y) contains supplementary material, which is available to authorized users.

Viral causes of hearing loss: a review for hearing health professionals

A number of viral infections can cause hearing loss. Hearing loss induced by these viruses can be congenital or acquired, unilateral or bilateral. Certain viral infections can directly damage inner ear structures, others can induce inflammatory responses which then cause this damage, and still others can increase susceptibility or bacterial or fungal infection, leading to hearing loss. Typically, virus-induced hearing loss is sensorineural, although conductive and mixed hearing losses can be seen following infection with certain viruses. Occasionally, recovery of hearing after these infections can occur spontaneously. Most importantly, some of these viral infections can be prevented or treated. For many of these viruses, guidelines for their treatment or prevention have recently been revised. In this review, we outline many of the viruses that cause hearing loss, their epidemiology, course, prevention, and treatment.

Contemporary perspectives on the pathophysiology of Meniere's disease: implications for treatment

PURPOSE OF REVIEW

Meniere's disease is characterized by episodic vertigo, fluctuating hearing loss, aural fullness and tinnitus. Endolymphatic hydrops, found on post-mortem examination, is the histologic hallmark. Recent research suggests that endolymphatic hydrops results from cytochemical perturbations of unknown etiology that lead to disturbance of the normal endolymphatic fluid homeostasis. This consequent hydropic state or the associated cytochemical perturbations appears to create a neurotoxic environment that ultimately leads to spiral ganglion cell death likely via the apoptotic mechanism. This review highlights some of the recent advances in the understanding of the pathophysiology of endolymphatic hydrops and progressive cochleovestibular deterioration, with emphasis placed on its potential therapeutic implications.

RECENT FINDINGS

Recent evidence supports that endolymphatic hydrops is possibly an epiphenomenon, and is preceded by perturbation of the normal ionic transport regulatory mechanisms. Furthermore, chronic cochleovestibular deterioration appears to be the result of an excitotoxic response to chronic hydrops. A recently described animal model, the Phex mouse, carrying a mutation in the Phex Hyp-Duk gene, provides a novel insight to genetically regulated postnatal endolymphatic hydrops and a useful tool to expand our understanding.

SUMMARY

Despite encouraging recent advances, there are considerable challenges that remain in the development of targeted therapeutic interventions that may offer new avenues of neuroprotection in known cases of Meniere's disease. These advances will hopefully provide pharmacotherapeutic interventions aimed at preventing progressive cochleovestibular dysfunction.

Expression and translocation of aquaporin-2 in the endolymphatic sac in patients with Meniere's disease

Meniere's disease, characterised by episodic vertigo, fluctuating hearing loss and tinnitus, can occur under conditions of stress. Its pathology was first revealed to be inner ear hydrops through temporal bone studies in 1938. Although its pathogenesis has been proposed to be a disorder of water transport in the inner ear, subsequently, it remains unsolved, until now. A recent study revealed that both plasma stress hormone, vasopressin (pAVP) and its receptor, V2 (V2R) expression in the inner ear endolymphatic sac were significantly higher in Meniere's patients. In the present study, to link V2R-related molecules and inner ear hydrops, we examined V2R-linked water channel molecule, aquaporin-2 (AQP2) expression and translocation in human endolymphatic sac. AQP2 mRNA expression in the endolymphatic sac was significantly higher in Meniere's patients by using real-time polymerase chain reaction, as further confirmed by western blotting. AQP2-like immunoreactivity (-LIR) was translocated from luminal to basolateral side with endosomal trapping in the endolymphatic sac at the time of AVP exposure in human endolymphatic sac tissue culture. The similar AQP2-LIR translocation was also demonstrated by forskolin and blocked by vasopressin/V2R specific antagonist, OPC31260 and protein kinase A (PKA) specific antagonists, H-89 and KT-5720. We concluded that in the pathogenesis of inner ear hydrops resulting in Meniere's attacks, pAVP elevation as a result of stress and subsequent V2R-cAMP-PKA-AQP2 activation and endosomal trapping of AQP2 in the endolymphatic sac, might be important as a basis of this disease. Further experimental and clinical studies are needed to better clarify the neuroscientific relationship between stress and Meniere's disease.

Plasma vasopressin and V2 receptor in the endolymphatic sac in patients with delayed endolymphatic hydrops

OBJECTIVE

There are some kinds of sicknesses provoked by inadequate adaptation to physical and/or psychogenic stress in daily life. Delayed endolymphatic hydrops (DEH) is an inner ear disease like Ménière's disease (MD) characterized by episodic vertigo in the setting of preexisting unilateral deafness that especially occurs in civilized people with a stressful lifestyle. Its otopathologic finding was demonstrated to be inner ear endolymphatic hydrops through a temporal bone study in 1976, as in the case with MD in 1938. To elucidate the relationship between stress and the inner ear, we examined the plasma antidiuretic stress hormone vasopressin (pAVP) and its type 2 receptor (V2R) expression in the endolymphatic sac in patients with DEH.

STUDY DESIGN

A prospective molecular biological study.

METHODS

Between 1998 and 2007, we enrolled 20 patients with ipsilateral DEH to examine their pAVP during remission from vertigo attacks. Plasma vasopressin was also examined in 87 patients with unilateral MD and 30 control patients with chronic otitis media. Using the real-time polymerase chain reaction method with tissue samples obtained during surgery, we examined V2R mRNA expression in the endolymphatic sac in 6 patients with ipsilateral DEH, 9 patients with unilateral MD, and 6 control patients with acoustic neuroma.

RESULTS

Plasma vasopressin (1.5 times versus controls; unpaired t test, p = 0.140) and V2R mRNA expression in the endolymphatic sac (35.8 times versus controls; unpaired t test, p = 0.002) were higher in patients with DEH compared with those with acoustic neuroma. There were no significant differences in pAVP or V2R expression in the endolymphatic sac between DEH and MD. Patients with DEH showed a significantly negative correlation between pAVP and V2R (Pearson test, r = -0.92, p = 0.009) as in those with MD (Pearson test, r = -0.68, p = 0.043).

CONCLUSION

Civilized people are frequently exposed to stress in their daily life, and pAVP can easily become elevated at any time. Therefore, a negative feedback system between pAVP and V2R in the endolymphatic sac may function for inner ear fluid homeostasis against stress-induced increases in pAVP. For the pathogenesis of endolymphatic hydrops resulting in vertigo attacks in patients with DEH as well as MD, pAVP may represent a matter of consequence, but V2R overexpression in the endolymphatic sac could be much more essential as a basis for these diseases.

Meniere's attacks occur in the inner ear with excessive vasopressin type-2 receptors

Meniere's disease is peculiar to humans and is characterised by episodic vertigo, fluctuating hearing loss and tinnitus, and attacks of the affliction occurring under conditions of stress. Its pathology was first revealed to be inner ear hydrops through temporal bone studies in 1938. Although subsequently proposed as a disorder of water metabolism in the inner ear, its pathogenesis remains unsolved. The present study aimed to assess the link between the inner ear pathology in Meniere's disease and vasopressin, an anti-diuretic stress hormone with a potential role in inner ear fluid homeostasis. Blood samples were obtained from Meniere's disease patients in the morning, before any surgical treatment, to examine plasma vasopressin (pAVP) levels, and then from inner ear tissue during surgical treatment, to examine vasopressin type-2 receptor (V2R) in the endolymphatic sac. pAVP and the relative V2R mRNA expression in the endolymphatic sac were examined using a real-time polymerase chain reaction. Relative cAMP activity in the endolymphatic sac was also examined using tissue culture and cAMP assay. Both pAVP (1.6-fold versus controls; P = 0.048) and inner ear V2R mRNA expression (41.5-fold versus controls; P = 0.022) were significantly higher in Meniere's patients. cAMP activity was basally up-regulated (2.1-fold versus controls) and cAMP sensitivity to vasopressin application was largely elevated (4.9-fold versus controls) in Meniere's patients. We conclude that, in the pathogenesis of inner ear hydrops, resulting in Meniere's attacks, elevation of pAVP levels (probably as a result of stress) may present as a matter of consequence, but susceptibility of the V2R-overexpressed and cAMP-hypersensitized inner ear to pAVP elevation might be essential as the basis of this disease. Further experimental and clinical studies are needed to better clarify the relationship between Meniere's disease and stress.

Expression of histamine receptors (H(1), H(2), and H(3)) in the rabbit endolymphatic sac: an immunohistochemical study

OBJECTIVE

The endolymphatic sac (ES) is part of the membranous labyrinth of the inner ear. Its central role in immunologic activity within the inner ear has been confirmed by numerous studies. The aim of this study was to investigate the expression of histamine receptors (H(1), H(2), H(3)) in the rabbit ES.

METHODS

A total of 10 healthy male New Zealand white rabbits weighing 2 to 3 kg were used in the experiments. For immunohistochemical studies, immunostaining was performed according to the avidin-biotin-peroxidase complex technique.

RESULTS

Serial sections of the ES of rabbits revealed the presence of H(1), H(2), and H(3) receptor immunoreactivity. Immunoreactive cells for all H(1), H(2), and H(3) were found in the epithelial and subepithelial layers of the duct and the proximal ES. In conclusion, this study showed the immunohistochemical localization of H(1), H(2), and H(3) receptors in the ES of rabbits. These receptors may be important in the homeostasis of the inner ear. In addition, they may be target receptors in the medical treatment of inner ear disorders such as endolymphatic hydrops.

Incidence of virus infection as a cause of Meniere?s disease or endolymphatic hydrops assessed by electrocochleography

Meniere's disease (MD) may follow viral infection such as by neurotropic viruses known to invade the endolymphatic sac (ES) and provoke endolymphatic hydrops (EH). The objective of this study was to investigate whether neurotropic viruses may cause infection of the inner ear and provoke EH. Antiviral immunoglobulin (IgG) assay against herpes simplex 1 (HSV1), herpes simplex 2 (HSV2), adenovirus (ADV), varicella zoster virus (VZV) and cytomegalovirus (CMV) were performed in 109 patients with an advanced stage of MD and compared with those obtained from 26 patients operated on because of vestibular schwannoma (VS), who served as a control group, to evaluate whether there is an association between the IgG levels and the ECoGs summating potential/action potential ratio (SP/AP ratio) in the MD group. In MD patients, the IgG titre against VZV and ADV were significantly higher than in the control (schwannoma) group. However, no correlation was found between the IgG levels against ADV and VZV with the SP/AP ratio. Neurotropic viruses such VZV and ADV may play a role in the pathogenesis of MD, despite the absence of association between the levels of IgG titres and the SP/AP ratio.