Histopathological and ultrastructural analysis of vestibular endorgans in Meniere's disease reveals basement membrane pathology

The dissociation between pathological caloric testing and a normal video head impulse test helps differentiate between Menière's disease, vestibular migraine, and other vestibular disorders: a confirmatory study in a large cohort of 2,101 patients

Vestibular migraine (VM) and Menière's disease (MD) are characterized by episodes of vertigo of similar duration. It is well known that differentiation between both diseases is not always possible based only on the patient history, physical examination, and audiological testing. In addition, the quantification of the vestibular function can also be helpful since, among patients with MD, there is often a dissociation between a normal/pseudo-normal video head impulse test (vHIT) and reduced caloric testing. The goal of this confirmatory study was to determine the sensitivity, specificity, and positive and negative predictive values (PPV and NPV) of this dissociation to differentiate between MD and VM as well as between MD and other vestibular diseases. We performed a retrospective analysis of 2,101 patients. The examination group consisted of 1,100 patients; of these, 627 (57%) had MD according to the diagnostic criteria of the Bárány Society and 473 (43%) had VM. The comparison group consisted of 1,001 patients with other peripheral, central, or functional vestibular disorders. Statistical analysis revealed the following findings for the dissociation: MD vs. VM: specificity: 83.5%, sensitivity: 58.9%, PPV: 82.6%, and NPV: 60.5%, and MD vs. all other vestibular disorders (VM plus others): specificity: 83.5%, sensitivity: 58.9%, PPV: 60.3%, and NPV: 82.7%. The dissociation between a normal vHIT and a reduced caloric response is due to the high specificity and PPV suited for the differentiation between MD and VM. This part of the study confirms previous findings in a large cohort of patients. When it comes to differentiating between MD and all observed vestibular disorders, if there is no dissociation, the diagnosis of MD is unlikely.

Lymphatic Vessels in the Inner Ear of Patients With Meniere Disease: A Novel Pathological Finding

Background

Meniere disease, characterized by intermittent episodes of vertigo, fluctuating sensorineural hearing loss, tinnitus, and aural pressure, is a common cause of vertigo in humans. The pathogenesis of Meniere disease remains unknown. The current study aimed to describe a novel pathological change discovered in the inner ears of patients with Meniere disease who underwent labyrinthectomy.

Methods

This retrospective case-control study was conducted with 21 patients with MD who underwent labyrinthectomy. A total of 15 patients diagnosed with acoustic neuroma or glomus jugular tumor were review over the same period of time as control. The clinical information of the patients and the pathological features of the membrane are described.

Results

The new pathological tissue was a morbid membrane structure sealing the round window, characterized by the formation of lymphatic capillaries. Histochemical and immunofluorescent staining was positive for D2-40, LYVE-1, podoplanin, and PROX1, which are the classical markers of the lymphatic vessels. Transmission electron microscopy revealed that the lymph capillaries lacked a typical basement membrane and that their ends were blind, composed of a single layer of endothelial cells with valval connection structures between adjacent capillary epithelial cells.

Conclusion

This is the first report of lymphatic vessels in the human inner ear, and this pathological structure is a completely new discovery. The lymphatic vessels may develop due to inflammation or decompensation of pressure in the inner ear, suggesting that the inner ear can reactively form lymphatic vessels in some inflammation and fluid flow-dependent pathological conditions. The current findings help in improving our understanding of the pathogenesis of Meniere disease.

Impact of endolymphatic hydrops on the function of the horizontal canal during caloric stimulation in Ménière's disease

PURPOSE

When a dizzy patient with episodic vertigo has an abnormal caloric and a normal video head impulse test (vHIT), this caloric-vHIT dissociation provides vital information for a diagnosis of Ménière's disease (MD). Endolymphatic hydrops (EH), a histological marker of MD, is hypothesized to be involved in the caloric-vHIT dissociation in MD through hydropic duct distension of the horizontal semicircular canal (SC). This study was designed to determine the impact of EH on the function of horizontal SC during caloric stimulation.

METHODS

Caloric test and vHIT were used to evaluate the function of horizontal SC every six months, annual magnetic resonance imaging (MRI) was used to evaluate the degree of EH size in the vestibule, and monthly vertigo and hearing evaluation was done for 12 months. EH shrinkage was defined as the size change of vestibular EH from significant to none.

RESULTS

Among 133 MD patients evaluated for eligibility, 67 patients with caloric-vHIT dissociation entered the study. Fifteen participants had EH shrinkage (G-I), while 52 participants had no remarkable EH change (G-II). Average values (IQR) of the maximum slow phase velocity in G-I and G-II were 29.6 (13.0-34.0) and 25.9 (17.3-31.3), respectively, at baseline, 26.1 (9.0-38.0) and 23.6 (18.0-28.3) at 12 months. Two-factor repeated-measures ANOVA showed no significant differences between the groups (P = 0.486). The values of vestibulo-ocular reflex gain of the horizontal SC in G-I and G-II remained above 0.8 during the study period.

CONCLUSIONS

EH detected by MRI shows limited correlation with caloric stimulation results.

Ménière's disease and allergy: Epidemiology, pathogenesis, and therapy

The etiology of Ménière's disease (MD) remains controversial. Allergies are potential extrinsic factors that, in conjunction with underlying intrinsic factors, may cause MD. The link between allergies and MD was first described in 1923. For nearly a century, studies have demonstrated a possible link between allergies and MD, even though a causal relationship has not been definitively determined. Previous reviews have mainly focused on clinical epidemiology studies of patients. In this review, we shed light on the association between allergies and MD not only in terms of its epidemiology, but also from an immunology, pathophysiology, and immunotherapy perspective in both patients and animal models. Patients with MD tend to have a high risk of comorbid allergies or an allergy history, showing positive allergy immunology characteristics. Other MD-related diseases, such as migraine, may also interact with allergies. Allergy mediators such as IgE may worsen the symptoms of MD. Deposits of IgE in the vestibular end organs indicate the ability of the inner ear to participate in immune reactions. Allergic challenges can induce vertigo in animals and humans. Anti-allergy therapy plays a positive role in patients with MD and animal models of endolymphatic hydrops.

Otolith Membrane Herniation, not Semicircular Canal Duct Dilation, Is Associated with Decreased Caloric Responses in Ménière's Disease

Ménière's disease (MD) is a debilitating disorder with unclear pathophysiology whose diagnosis often relies on clinical judgment rather than objective testing. To complicate matters further, a dissociation has emerged between two vestibular function tests commonly used in patients with MD to examine the same end-organ (the semicircular canals): the caloric test and video head impulse testing (vHIT). Caloric responses are often abnormal, while vHIT results remain normal. Explaining this dissociation could reveal novel insights into MD pathophysiology. Here, we conduct a histopathological study using temporal bone specimens (N = 58, 21 MD-affected ears and 37 age-matched controls) and their clinical testing data to examine current hypotheses aimed at this dissociation. We find otolith membrane herniation into the horizontal semicircular canal in 69% of MD ears, with 90% of these ears demonstrating a diminished caloric response. No ears with a normal response had this herniation. Moreover, we evaluated the semicircular canals for endolymphatic hydrops, which had been hypothesized to contribute to the dissociation, and found no evidence of duct dilation/hydrops. We did, however, note a potentially novel morphologic finding-smaller bony labyrinth cross-sectional diameters/areas in some MD ear canals compared to controls, suggesting relative size of the membranous duct to the bony canal rather than absolute size may be of importance. Taken together, this study refines hypotheses on the vestibular test dissociation in MD, holding diagnostic implications and expanding our understanding of the mechanisms underlying this enigmatic disease.

A Portrait of Menière's Disease Using Contemporary Hearing and Balance Tests

OBJECTIVE

Menière's disease (MD) is characterized by recurrent vertigo and fluctuating aural symptoms. Diagnosis is straightforward in typical presentations, but a proportion of patients present with atypical symptoms. Our aim is to profile the array of symptoms patients may initially present with and to analyze the vestibular and audiological test results of patients with a diagnosis of MD.

DESIGN

A retrospective study of patient files.

SETTING

A tertiary, neuro-otology clinic Royal Prince Alfred Hospital, Sydney, Australia.

METHOD

We identified 375 patients. Their history, examination, vestibular-evoked myogenic potentials (VEMP), video head-impulse test, canal-paresis on caloric testing, subjective visual horizontal (SVH), electrocochleography, ictal nystagmus, and audiometry were assessed.

RESULTS

Atypical presenting symptoms were disequilibrium (n = 49), imbalance (n = 13), drop-attacks (n = 12), rocking vertigo (n = 2), and unexplained vomiting (n = 3), nonspontaneous vestibular symptoms in 21.6%, fluctuation of aural symptoms only (46%), and headaches (31.2%). Low velocity, interictal spontaneous-nystagmus in 13.3% and persistent positional-nystagmus in 12.5%. Nystagmus recorded ictally in 90 patients was mostly horizontal (93%) and of high velocity (48 ± 34°/s). Testing yielded abnormal caloric responses in 69.6% and abnormal video head impulse test 12.7%. Air-conducted cervical VEMPs were abnormal in 32.2% (mean asymmetry ratio [AR] 30.2 ± 46.5%) and bone-conducted ocular VEMPs abnormal in 8.8% (AR 11.2 ± 26.8%). Abnormal interictal SVH was in 30.6%, (ipsiversive n = 46 and contraversive n = 19). Mean pure-tone averages 50 dB ± 23.5 and 20 dB ± 13 for affected and unaffected ears.

CONCLUSION

Menière's disease has a distinctive history, but atypical presentations with normal vestibular function and hearing are a diagnostic challenge delaying treatment initiation.

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.

Epithelial-Mesenchymal Transition Participates in the Formation of Vestibular Flat Epithelium

The vestibular sensory epithelium of humans and mice may degenerate into a layer of flat cells, known as flat epithelium (FE), after a severe lesion. However, the pathogenesis of vestibular FE remains unclear. To determine whether the epithelial–mesenchymal transition (EMT) participates in the formation of vestibular FE, we used a well-established mouse model in which FE was induced in the utricle by an injection of streptomycin into the inner ear. The mesenchymal and epithelial cell markers and cell proliferation were examined using immunofluorescence staining and quantitative reverse transcription polymerase chain reaction (qRT-PCR). The function of the EMT was assessed through transcriptome microarray analysis. The results demonstrated that mesenchymal cell markers (α-SMA, S100A4, vimentin, and Fn1) were upregulated in vestibular FE compared with the normal utricle. Robust cell proliferation, which was absent in the normal status, was observed in the formation of FE. Microarray analysis identified 1,227 upregulated and 962 downregulated genes in vestibular FE. Gene Ontology (GO) analysis revealed that differentially expressed genes (DEGs) were highly associated with several EMT-related GO terms, such as cell adhesion, cell migration, and extracellular matrix. Pathway enrichment analysis revealed that DEGs were enriched in the EMT-related signaling pathways, including extracellular matrix (ECM)-receptor interaction, focal adhesion, PI3K/Akt signaling pathway and cell adhesion molecule. Protein–protein interaction networks screened 20 hub genes, which were Akt, Casp3, Col1a1, Col1a2, Fn1, Hgf, Igf1,Il1b, Irs1, Itga2, Itga5, Jun, Mapk1, Myc, Nras, Pdgfrb, Tgfb1, Thbs1, Trp53, and Col2a1. Most of these genes are reportedly involved in the EMT process in various tissues. The mRNA expression level of hub genes was validated using qRT-PCR. In conclusion, the present study indicates that EMT plays a significant role in the formation of vestibular FE and provides an overview of transcriptome characteristics in vestibular FE.

[Dissociation of the results of caloric and video head impulse tests as a marker of Meniere's disease]

The study of vestibular function in patients with Meniere's disease (MD) is an urgent task, since it influences the choice of treatment tactic. We evaluated the results of caloric and video head impulse (vHIT) tests in 76 patients who met the clinical criteria for significant Meniere's disease (AAO-HNS modified by the Barany Society, 2015). Dissociation of the results of caloric and vHIT tests is observed in the majority (74%) of patients with MD: at normal gain, according to vHIT data, hypofunction of peripheral vestibular structures is recorded according to the caloric test (KASL 47 ± 7.8%). In patients with MD, vestibular dysfunction is observed mainly at low frequencies (0.003 Hz), therefore vHIT, which allows assessing horizontal semicircular canal function at high frequencies (3-5 Hz), is not an optimal study for assessing the degree of vestibular dysfunction in patients with MD.

Clinical Implication of Caloric and Video Head Impulse Tests for Patients With Enlarged Vestibular Aqueduct Presenting With Vertigo

Background: By examining the clinical features and results of video head impulse test (vHIT) and caloric tests in patients with enlarged vestibular aqueduct (EVA) presenting with vertigo, we aimed to investigate the function of angular vestibulo-ocular reflex (VOR) and its clinical implications.

Methods: Nine patients with EVA manifesting with vertigo were enrolled. The medical history, audiological examination, imaging, and the results of the caloric test and the vHIT were analyzed.

Results: Of the nine patients with EVA (eight bilateral and one unilateral case), five were pediatric cases. All 17 ears exhibited sensorineural hearing loss (SNHL). Enlarged vestibular aqueduct patients can present with recurrent (seven cases) or single (two cases) vertigo attack, trauma-induced (two cases), or spontaneous (seven cases) vertigo. Diminished caloric responses were observed in 77.8% (7/9) of the patients (four cases unilaterally and three bilaterally), while unilateral abnormal vHIT results in 11.1% (1/9) patients. Abnormal caloric and normal horizontal vHIT responses were found in 66.7% (6/9) of EVA patients.

Conclusions: Vestibular manifestations in EVA are diverse. Enlarged vestibular aqueduct patients with vertigo can present with a reduced caloric response and normal horizontal vHIT, and this pattern of angular VOR impairment was also found in other hydropic ear diseases.

Vestibulo-ocular reflex tests may reflect unilateral Ménière disease progression: A cross-sectional study

Vestibular disorders can manifest several patterns of horizontal vestibulo-ocular reflex (VOR) impairment, which can be detected by caloric test and video head impulse test (vHIT). Several studies have examined the patterns of caloric-vHIT response in Ménière disease (MD). The purpose of this study was to investigate the diversity of caloric-vHIT response and its related factors in unilateral MD patients. We also explore the possibility of assessing the progression of unilateral MD by using the horizontal VOR tests.Ninety-eight patients with unilateral MD were enrolled and underwent a battery of audio-vestibular evaluations, including the pure tone audiogram, caloric test, and horizontal vHIT. Some patients received the electrocochleography and glycerol test. The combined results of caloric test and horizontal vHIT were categorized qualitatively into 4 patterns: Pattern I: normal caloric and vHIT responses; Pattern II: abnormal caloric and normal vHIT responses; Pattern III: normal caloric and abnormal vHIT response; and Pattern IV: abnormal caloric and vHIT responses. The abnormal caloric results were semi-quantitatively subdivided into sub-patterns as mild, moderate, and severe abnormality. The associations between these patterns/sub-patterns and related factors were analyzed.Pattern I was found in 35 cases (35.7%), Pattern II in 57 (58.2%), and Pattern IV in 6 (6.1%). No patient had Pattern III. No significant differences were found between the patterns/sub-pattern distribution and age, electrocochleography, and glycerol test results. Disease duration was not associated with the pattern distribution, while remained a relation with sub-pattern distribution. The pattern/sub-pattern distribution varied significantly across MD stages. The proportion of pattern II or pattern IV increased with the stage of unilateral MD.MD can manifest several patterns of horizontal VOR impairment, of which the impaired caloric response with normal vHIT is the most common pattern. With the progression of unilateral MD, the caloric-vHIT pattern tends to shift, which may reflect the deterioration of endolymphatic hydrops and vestibular hair cells impairments.

Research progress on flat epithelium of the inner ear

Sensorineural hearing loss and vertigo, resulting from lesions in the sensory epithelium of the inner ear, have a high incidence worldwide. The sensory epithelium of the inner ear may exhibit extreme degeneration and is transformed to flat epithelium (FE) in humans and mice with profound sensorineural hearing loss and/or vertigo. Various factors, including ototoxic drugs, noise exposure, aging, and genetic defects, can induce FE. Both hair cells and supporting cells are severely damaged in FE, and the normal cytoarchitecture of the sensory epithelium is replaced by a monolayer of very thin, flat cells of irregular contour. The pathophysiologic mechanism of FE is unclear but involves robust cell division. The cellular origin of flat cells in FE is heterogeneous; they may be transformed from supporting cells that have lost some features of supporting cells (dedifferentiation) or may have migrated from the flanking region. The epithelial-mesenchymal transition may play an important role in this process. The treatment of FE is challenging given the severe degeneration and loss of both hair cells and supporting cells. Cochlear implant or vestibular prosthesis implantation, gene therapy, and stem cell therapy show promise for the treatment of FE, although many challenges remain to be overcome.

Usefulness of Video Head Impulse Test Results in the Identification of Meniere's Disease

Meniere's disease (MD) is an inner ear disorder inducing tinnitus, aural fullness, sensorineural hearing loss, and vertigo episodes. In the past few years, efforts have been made to develop objective measures able to distinguish MD from other pathologies. Indeed, some authors investigated electrophysiological measures, such as electrocochleography and vestibular evoked myogenic potentials or imaging techniques. More recently, the video head impulse test (vHIT) was developed to assess the vestibulo-ocular reflex (VOR). In the last few years, authors aimed at identifying how vHIT may help to identify MD. The objective of this manuscript is to review the different vHIT results in MD patients. We will discuss the usefulness of these findings in the identification of MD, how these results may be explained by pathophysiological mechanisms associated with MD, and finally provide directions for future studies.

Vestibular and audiological findings in the Alport syndrome

Alport syndrome (AS) is caused by mutations in collagen IV, which is widespread in the basement membranes of many organs, including the kidneys, eyes, and ears. Whereas the effects of collagen IV changes in the cochlea are well known, no changes have been described in the posterior labyrinth. The aim of this study was to investigate both the auditory and the vestibular function of a group of individuals with AS. Seventeen patients, aged 9-52, underwent audiological tests including pure-tone and speech audiometry, immittance test and otoacoustic emissions and vestibular tests including video head impulse test, rotatory test, and vestibular evoked myogenic potentials. Hearing loss affected 25% of the males and 27.3% of the females with X-linked AS. It was sensorineural with a cochlear localization and a variable severity. 50% of the males and 45.4% of the females had a hearing impairment in the high-frequency range. Otoacoustic emissions were absent in about one-third of the individuals. A peripheral vestibular dysfunction was present in 75% of the males and 45.4% of the females, with no complaints of vertigo or dizziness. The vestibular impairment was compensated and the vestibulo-ocular reflex asymmetry was more evident in rotatory tests carried out at lower than higher speeds; a vestibular hypofunction was present in all hearing impaired ears although it was also found in subjects with normal hearing. A posterior labyrinth injury should be hypothesized in AS even when the patient does not manifest hearing disorders or evident signs of renal failure.

Comparison of the video head impulse test results with caloric test in patients with Meniere's disease and other vestibular disorders

Background: The caloric test has been used to evaluate the semi-circular canal function for decades. In 2009, the video head impulse test (vHIT) was introduced, which can be used to evaluate the semi-circular canal function within a short time. Although both tests examine the semi-circular canal, the stimulation methods differ and it is unclear whether the vHIT is equivocal to the caloric test.Aims/objectives: This study aimed to discern the differences between the vHIT and caloric test.Material and methods: This study comprised 112 patients with vertigo who visited the vertigo/dizziness centre at our university hospital. Each of these patients underwent a caloric test and vHIT within the same day, and their results were compared. Additionally, an electrocochleography (EcoG) examination, glycerol test (G test), and MRI (performed 4 h after an intravenous gadolinium injection) were conducted to evaluate the influence of endolymphatic hydrops (EH) on the caloric test and vHIT results.Results: Differences in the caloric test and vHIT results, among those with and without EH, were observed in 66.7 and 35.3% of patients, respectively.Conclusions and significance: EH resulted in a difference in results between the caloric test and vHIT. Activated hair cell type may also be implicated.

Menière's Disease and Caloric Stimulation: Some News from an Old Test

OBJECTIVES

The aim of the present study was to improve the instrumental diagnosis of assessing Menière's disease (MD) if the frequency and slow-phase velocity (SPV) of the thermally induced nystagmus analyzed through the caloric vestibular test (CVT) showed different alterations in relationship with an increasing severity of the cochlear involvement.

MATERIALS AND METHODS

The study retrospectively analyzed the CVT results of 72 patients affected by unilateral "definite MD" according to the 2015 Barany Society Diagnostic Criteria and treated only conservatively.

RESULTS

There were 7 (9.72%) patients in stage 1, 27 (37.50%) in stage 2, 35 (48.61%) in stage 3, and 3 (4.16%) in stage 4. The canal paresis (CP) calculated through the frequency of the thermally induced nystagmus on the affected side increased in more severe stages (p=0.033). Conversely, the CP calculated through the SPV was not significantly different among the stages showing abnormal values even in the early phases of the disease (71% in stage 1, 81% in stage 2, 91% in stage 3, and 100% in stage 4), exclusively on the affected side.

CONCLUSION

Abnormalities of the thermally induced nystagmus on the affected side characterize most patients with MD, but only "SPV" alterations are common in the early stages. An increasing severity of the cochlear involvement progressively reflects also on the "frequency" parameter. Detecting a dissociation between these two parameters could represent an instrumental marker of the early forms of MD. Cite this article as: Cerchiai N, Navari E, Miccoli M, Casani AP. Menière's Disease and Caloric Stimulation: Some News from an Old Test. J Int Adv Otol 2019; 15(3): 442-6.

The Price of Immune Responses and the Role of Vitamin D in the Inner Ear

OBJECTIVE

In this review the authors discuss evidence from the literature concerning vitamin D and temporal bone diseases (benign paroxysmal positional vertigo [BPPV], Menière's disease [MD], vestibular neuritis, idiopathic facial paralysis, idiopathic acute hearing loss). Common features shared by Menière's disease, glaucoma, and the possible influence by vitamin D are briefly discussed.

DATA SOURCES, STUDY SELECTION

Publications from 1970 until recent times have been reviewed according to a keyword search (see above) in PubMed.

CONCLUSIONS

MD, BPPV, vestibular neuritis, idiopathic facial paralysis, idiopathic acute hearing loss may all have several etiological factors, but a common feature of the current theories is that an initial viral infection and a subsequent autoimmune/autoinflammatory reaction might be involved. Additionally, in some of these entities varying degrees of demyelination have been documented. Given the immunomodulatory effect of vitamin D, we postulate that it may play a role in suppressing an eventual postviral autoimmune reaction. This beneficial effect may be enhanced by the antioxidative activity of vitamin D and its potential in stabilizing endothelial cells. The association of vitamin D deficiency with demyelination has already been established in other entities such as multiple sclerosis and experimental autoimmune encephalitis. Mice without vitamin D receptor show degenerative features in inner ear ganglia, hair cells, as well as otoconia. The authors suggest further studies concerning the role of vitamin D deficiency in diseases of the temporal bone. Additionally, the possible presence and degree of demyelination in these entities will have to be elucidated more systematically in the future.

Dissociation of Caloric and Video Head Impulse Tests in Patients With Delayed Endolymphatic Hydrops

Delayed endolymphatic hydrops (DEH) represents a rare clinical entity characterized by intermittent vertigo attacks mimicking those of Ménière's disease (MD) in a patient with a prior sensorineural hearing loss. Some vestibular tests have been employed in patients with DEH. These tests provide useful diagnostic information and facilitate clinical decision-making. Here, we retrospectively studied the features of video head impulse test (vHIT) and examined its relationship with caloric test used in DEH patients. Included in this study were 17 patients with ipsilateral DEH and 2 with contralateral DEH. Among them, 73.7% (14/19) showed abnormal caloric test response (76.5% in ipsilateral DEH and 50% in contralateral DEH). Meanwhile, only 15.8% (3/19) of patients yielded abnormal horizontal vHIT results (11.8% in ipsilateral DEH and 50% in contralateral DEH). Abnormal caloric response in the presence of a preserved vHIT was common in DEH patients, especially those with ipsilateral DEH. This dissociation might be a distinctive pattern of vestibular deficit in DEH.

Investigations of the Microvasculature of the Human Macula Utricle in Meniere's Disease

The integrity and permeability of the blood labyrinthine barrier (BLB) in the inner ear is important to maintain adequate blood supply, and to control the passage of fluids, molecules and ions. Identifying the cellular and structural components of the BLB, the vascular endothelial cells (VECs), pericytes, and the perivascular basement membrane, is critical to understand the pathophysiology of the inner ear microvasculature and to design efficient delivery of therapeutics across the BLB. A recent study of the normal and pathological ultrastructural changes in the human macula utricle microvasculature demonstrated that the VECs are damaged in Meniere’s disease (MD), and further studies identified oxidative stress markers (iNOS and nitrotyrosine) in the VECs. Using fluorescence microscopy, the microvasculature was studied in the macula utricle of patients diagnosed with MD that required transmastoid labyrinthectomy for intractable vertigo (n = 5), and patients who required a translabyrinthine approach for vestibular schwannoma (VS) resection (n = 3). Normal utricles (controls) were also included (n = 3). VECs were identified using rabbit polyclonal antibodies against the glucose transporter-1 (GLUT-1) and pericytes were identified using mouse monoclonal antibodies against alpha-smooth muscle actin (α-SMA). Immunofluorescence (IF) staining was made in half of the utricle and flat mounted. The other half was used to study the integrity of the BLB using transmission electron microscopy (TEM). GLUT-1-IF, allowed delineation of the macula utricle microvasculature (located in the stroma underneath the sensory epithelia) in both MD and VS specimens. Three sizes of vessels were present in the utricle vasculature: Small size (<15 μm), medium size (15–25 μm) and large size >25 μm. α-SMA-IF was present in pericytes that surround the VECS in medium and thick size vessels. Thin size vessels showed almost no α-SMA-IF. AngioTool software was used for quantitative analysis. A significant decreased number of junctions, total vessel length, and average vessel length was detected in the microvasculature in MD specimens compared with VS and control specimens. The deeper understanding of the anatomy of the BLB in the human vestibular periphery and its pathological changes in disease will enable the development of non-invasive delivery strategy for the treatment of hearing and balance disorders.

Subcellular Abnormalities of Vestibular Nerve Morphology in Patients With Intractable Meniere's Disease

Objective: Few studies so far have focused on the retrocochlear lesions in Meniere's disease (MD). This study aims to investigate pathological alterations in the central portion of the vestibular nerve (VN) in patients with intractable Meniere's disease (MD) and to explore retrocochlear lesions and their relationship with disease severity. Methods: Eight MD patients with refractory vertigo received vestibular neurectomy via a retrosigmoid or translabyrinthine approach. Segments of VN were carefully removed and immediately fixed for histopathological examination. Five VN specimens were examined by light microscopy after hematoxylin/eosin staining; three specimens were extensively analyzed using transmission electron microscopy, to identify VN ultrastructural lesions. Correlations between lesions and patient clinical characteristics were examined. Results: Histopathological examination revealed evidence of various types of chronic VN impairment, including the formation of corpora amylacea (CA), axon atrophy, and severe damage to the myelin sheath. Electron microscopy revealed membranous whorls within dilated Schmidt-Lanterman incisures, the formation of myeloid bodies, dysmyelination, and demyelination. Unexpectedly, we observed a positive correlation between the density of CA in VN tissue and the duration of disease, as well as the degree of hearing impairment, independent of age. Conclusion: Our findings indicate that deformation of subcellular organelles in the central portion of the VN is one of the key pathological indicators for the progressive severity and intractability of vertigo and support a vestibular nerve degeneration.

Fluctuating Sensorineural Hearing Loss

BACKGROUND

Several otologic conditions can present with fluctuating sensorineural hearing loss, including Ménière's disease, autoimmune inner ear disease, and enlarged vestibular aqueduct. Although these 3 etiologies vary greatly, distinguishing between these conditions at initial presentation can be challenging. Furthermore, initial treatment of these conditions is often similar. In this review, we discuss historical and current perspectives on diagnosis and treatment of these conditions.

SUMMARY

A literature search was performed regarding fluctuating hearing loss, and current treatment of these etiologies of fluctuating hearing loss was summarized. Immediate measures at the onset of acute hearing loss include corticosteroid therapy, while preventative and chronic therapies, which can limit disease severity and frequency, vary based on the specific condition treated. Key Messages: Fluctuating hearing loss can represent a range of pathologies, but the precise etiology may not be clear at initial presentation. Timely treatment and long-term follow-up, along with appropriate diagnostics, are necessary to optimize long-term hearing.

Results in caloric test, video head impulse test and inner ear MRI in patients with Ménière's disease

OBJECTIVE

Our aim was to elucidate relationships between results from the caloric test (c-test), video Head Impulse Test (vHIT) and inner ear gadolinium-enhanced MRI (ieMRI) in patients with endolymphatic hydrops (EH), especially patients with Ménière's disease (MD).

METHODS

We managed 1789 successive patients at the Vertigo/Dizziness Center in Nara Medical University from May 2014 to December 2018. After providing informed consent for vertigo/dizziness examinations, 281 patients were hospitalized to check their inner ear function for proper diagnosis and treatment. Then 76 participants underwent the c-test, vHIT and ieMRI. Among these 76 cases, 20 were diagnosed with MD (20/76; 26.3%) and 56 were non-MD (56/76; 73.7%) according to the 2015 diagnostic guideline of the International Classification of Vestibular Disorders. The MD group included 15 unilateral and 5 bilateral cases. The non-MD group included 22 benign paroxysmal positional vertigo, 10 vestibular neuritis, 8 sudden deafness with vertigo, 6 orthostatic dysregulation, 4 vestibular neuropathy and 6 others. Results in these examinations in the side of an active lesioned inner ear were representative in each peripheral case.

RESULTS

Twenty-nine of the 76 patients (38.1%) showed discrepant results between the c-test (outside of normal range) and vHIT (within normal range). Twenty-two of 76 patients (28.9%) had a positive EH sign on ieMRI. The c-test/vHIT discrepancy percentage in MD (14/20; 70.0%) was significantly higher than that in non-MD (15/56; 26.8%) (p=0.00179). The positive EH sign in ieMRI percentage in MD (15/20; 75.0%) was significantly higher than that in non-MD (7/56; 12.5%) (p=0.0015). There was a significant positive relationship between the c-test/vHIT discrepancy and the positive EH sign (p=0.00058) in all 76 cases combined. However, there was no significant relationship between c-test/vHIT discrepancy and positive EH sign (p=0.13) in the 20 MD cases. Considering the 15 unilateral and 5 bilateral MD cases, the c-test/vHIT discrepancy was observed in 14 of the 25 affected ears. Positive signs of vestibular EH herniation into the cupula in the lateral semicircular canal was seen in 14 of the 25 MD ears. There was significant relationship between the c-test/vHIT discrepancy and EH herniation (p=0.0012) in MD ears.

CONCLUSION

The present results suggest that patients with MD could have inner ear EH significantly more often than those with non-MD. In cases with MD, a positive EH sign on ieMRI did not always indicate a c-test/vHIT discrepancy; both findings may occur due to herniation of vestibular EH adjacent to the lateral semicircular canal.

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.

Vertical head impulse and caloric are complementary but react opposite to Meniere's disease hydrops

OBJECTIVES/HYPOTHESIS

Meniere's disease (MD) patients can show normal head impulses despite poor caloric test results. This study aimed to investigate the discrepancy in the vestibulo-ocular reflex (VOR) in MD patients and whether endolymphatic hydrops (EH) influence the VOR.

STUDY DESIGN

Prospective, cross-sectional observational study.

METHODS

Ninety MD patients were enrolled. Neuro-otological testing, including a video head impulse test (vHIT) of all semicircular canals (SCs), and gadolinium-enhanced inner ear magnetic resonance imaging were performed. The vestibular EH volume was quantitatively evaluated by processing magnetic resonance images.

RESULTS

Abnormal vHIT results in MD patients were found most frequently in the posterior (44.4%) SCs, followed by the horizontal (13.3%) and anterior (10%) SCs. Canal paresis (CP) was assessed using the vHIT and the caloric test, and results were not significant when vHIT responses were assessed as CP only using the horizontal SC. The difference in the vestibular EH between the presence and absence of CP was not significant if assessed using the vHIT (P = .5591), but it was statistically different if assessed using the caloric test (P = .0467).

CONCLUSIONS

The contradictory reaction of VOR in MD patients may result from the high specificity but low sensitivity of CP in the horizontal vHIT. EH volume in the vestibule affects the caloric response but does not affect the vHIT response.

LEVEL OF EVIDENCE

2b Laryngoscope, 129:1660-1666, 2019.

Focal Degeneration of Vestibular Neuroepithelium in the Cristae Ampullares of Three Human Subjects

BACKGROUND

We report a unique pattern of focal degeneration of the neuroepithelium of cristae ampullares, thick subepithelial extracellular deposits, and neural degeneration in three humans.

OBJECTIVE

To characterize the pattern of vestibular degeneration and measure the thickness of subepithelial deposits in these three cases and controls.

METHODS

The subepithelial deposits of vestibular end organs in three subject cases and controls were studied using hematoxylin and eosin, periotic acid-Schiff, Gomori trichrome staining, and immunostaining for antineurofilament, antimyosin VIIa, and anticollagen 4a1. The thickness of deposit as measured by light microscopy was compared with that of control groups (age-matched controls, patients with unilateral Menière's disease, vestibular neuritis, cupulolithiasis, severe nonfocal degeneration of the vestibular neuroepithelium, and Alport syndrome). The correlation of thickness of deposits with age from 0 to 100 years was also investigated.

RESULTS

Focal loss of hair cells in the neuroepithelium, thick subepithelial deposits, and degeneration of subepithelial dendrites and Scarpa's ganglion were found in all three cristae of three subject cases. Immunostaining demonstrated a decrease of afferent neural fibers in the cristae and focal fragmentation of the basement membrane adjacent to the deposits. The thickness of the subepithelial deposits in three cristae of three subject cases was significantly greater than that of all controls. In the three cristae of normal controls, the thickness of deposits demonstrated a positive correlation with age.

CONCLUSION

Although both age and degeneration of the vestibular neuroepithelium may be associated with the thickness of the subepithelial deposits, in this unique pattern of degeneration, the thickness of the subepithelial deposits was significantly greater than that in all controls.

Oxidative Stress in the Blood Labyrinthine Barrier in the Macula Utricle of Meniere's Disease Patients

The blood labyrinthine barrier (BLB) is critical in the maintenance of inner ear ionic and fluid homeostasis. Recent studies using imaging and histopathology demonstrate loss of integrity of the BLB in the affected inner ear of Meniere's disease (MD) patients. We hypothesized that oxidative stress is involved in the pathogenesis of BLB degeneration, and to date there are no studies of oxidative stress proteins in the human BLB. We investigated the ultrastructural and immunohistochemical changes of the BLB in the vestibular endorgan, the macula utricle, from patients with MD (n = 10), acoustic neuroma (AN) (n = 6) and normative autopsy specimens (n = 3) with no inner ear disease. Each subject had a well-documented clinical history and audiovestibular testing. Utricular maculae were studied using light and transmission electron microscopy and double labeling immunofluorescence. Vascular endothelial cells (VECs) were identified using isolectin B4 (IB4) and glucose-transporter-1 (GLUT-1). Pericytes were identified using alpha smooth muscle actin (αSMA) and phalloidin. IB4 staining of VECS was consistently seen in both AN and normative. In contrast, IB4 was nearly undetectable in all MD specimens, consistent with the significant VEC damage confirmed on transmission electron microscopy. GLUT-1 was present in MD, AN, and normative. αSMA and phalloidin were expressed consistently in the BLB pericytes in normative, AN specimen, and Meniere's specimens. Endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and nitrotyrosine were used as markers of oxidative stress. The VECs of the BLB in Meniere's had significantly higher levels of expression of iNOS and nitrotyrosine compared with normative and AN specimen. eNOS-IF staining showed similar patterns in normative and Meniere's specimens. Microarray-based gene expression profiling confirmed upregulation of iNOS mRNA from the macula utricle of Meniere's patients compared with AN. Nitrotyrosine, a marker recognized as a hallmark of inflammation, especially when seen in association with an upregulation of iNOS, was detected in the epithelial and stromal cells in addition to VECs in MD. Immunohistochemical and ultrastructural degenerative changes of the VEC suggest that these cells are the primary targets of oxidative stress, and pericyte pathology including degeneration and migration, likely also plays a role in the loss of integrity of the BLB and triggering of inflammatory pathways in MD. These studies advance our scientific understanding of oxidative stress in the human inner ear BLB and otopathology.

Video-head impulse test results in patients with Menière's disease related to duration and stage of disease

BACKGROUND

The video-head impulse test employs the vestibulo-ocular reflex (VOR) to assess vestibular function. To this day, no consensus has been reached among scientists in terms of whether or not vHIT results change in MD patients as the disease progresses.

OBJECTIVE

To assess whether the vHIT is more often abnormal in later stages of MD compared to earlier stages.

METHODS

We retrospectively analyzed patients with 'definite' MD who had undergone a vHIT and caloric test between 2012 and 2015. Patients were evaluated based on duration of disease in years (≤1, >1≤5, >5≤10, >10) and stage of disease (stage I and II versus III and IV). For the vHIT, an abnormal vestibulo-ocular reflex was defined as a gain cut-off value of≤0.8 and presence of correction saccades including subanalyses using a cut-off value of≤0.9.

RESULTS

In 89 definite MD patients (42 (47%) male, mean age 55±5 (SD)), data on both the caloric test and the vHIT were available. The risk of an abnormal vHIT was 25% in patients with a duration of disease over 10 years compared to 22% in the patients with a disease duration of 10 years or less (risk difference 3%, 95% CI:- 28% to 35%), p = 0.82). The risk for an abnormal vHIT in the Stage I and Stage II was 17% compared to 26% in Stage III and IV (risk difference 9%, 95% CI:- 30% to 11%). When using a cut-off value of 0.9 we also did not demonstrate a relationship between the duration of disease and the proportion of abnormal vHIT test results.

CONCLUSIONS

There is no relationship between the proportion of abnormal vHIT test results in patients with MD in either duration or stage of disease.

Morphological correlation between caloric tests and vestibular hydrops in Ménière's disease using intravenous Gd enhanced inner ear MRI

The purpose of this study was to prove the hypothesis that caloric response in Ménière's disease (MD) is reduced by hydropic expansion of the vestibular labyrinth, not by vestibular hypofunction, by evaluating the correlation morphologically using an intravenous Gadolinium (IV-Gd) inner ear MRI. In study I, the prevalence of abnormal video Head Impulse Test (vHIT) results among the patients with definite unilateral MD (n = 24) and vestibular neuritis (VN) (n = 22) were investigated. All patients showed abnormal canal paresis (CP) (> 26%) on caloric tests. The prevalence of abnormal vHIT in patients with abnormal CP was significantly lower in MD patients (12.5%) than that in VN patients (81.8%) (p < 0.001). In study II, morphological correlation between caloric tests and vestibular hydrops level was evaluated in unilateral MD patients (n = 16) who had normal vHIT results. Eleven patients (61%) had abnormal CP. After taking the images of IV-Gd inner ear MRI, the vestibular hydrops ratio (endolymph volume/total lymph volume = %VH) was measured. In addition, the relative vestibular hydrops ratio (%RVH = (%VHaffected ear-%VHunaffected ear) / (%VHaffected ear + %VHunaffected ear)) was calculated. Each ratio (%VH and %RVH) was compared with average peak slow phase velocity (PSPV) and CP, respectively. In the MD patients, %VH of the affected ear correlated significantly with mean PSPV on the same side (rs = -0.569, p = 0.024), while %RVH correlated significantly with CP (rs = 0.602, p = 0.014). In most MD patients (87.5%) compared to VN patients, vHIT results were normal even though the caloric function was reduced. In addition, the reduced caloric function with normal vHIT was related to the severity of the vestibular hydrops measured by the IV-Gd inner ear MRI. These findings concluded that the abnormal caloric tests with normal vHIT in MD indicated severe endolymphatic hydrops rather than vestibular hypofunction.

Severe streptomycin ototoxicity in the mouse utricle leads to a flat epithelium but the peripheral neural degeneration is delayed

The damaged vestibular sensory epithelium of mammals has a limited capacity for spontaneous hair cell regeneration, which largely depends on the transdifferentiation of surviving supporting cells. Little is known about the response of vestibular supporting cells to a severe insult. In the present study, we evaluated the impact of a severe ototoxic insult on the histology of utricular supporting cells and the changes in innervation that ensued. We infused a high dose of streptomycin into the mouse posterior semicircular canal to induce a severe lesion in the utricle. Both scanning electron microscopy and light microscopy of plastic sections showed replacement of the normal cytoarchitecture of the epithelial layer with a flat layer of cells in most of the samples. Immunofluorescence staining showed numerous cells in the severely damaged epithelial layer that were negative for hair cell and supporting cell markers. Nerve fibers under the flat epithelium had high density at the 1 month time point but very low density by 3 months. Similarly, the number of vestibular ganglion neurons was unchanged at 1 month after the lesion, but was significantly lower at 3 months. We therefore determined that the mouse utricular epithelium turns into a flat epithelium after a severe lesion, but the degeneration of neural components is slow, suggesting that treatments to restore balance by hair cell regeneration, stem cell therapy or vestibular prosthesis implantation will likely benefit from the short term preservation of the neural substrate.

The blood labyrinthine barrier in the human normal and Meniere's disease macula utricle

The ultrastructural organization of the blood labyrinthine barrier (BLB) was investigated in the human vestibular endorgan, the utricular macula, using postmortem specimens from individuals with documented normal auditory and vestibular function and surgical specimens from patients with intractable Meniere’s disease. Transmission electron microscopic analysis of capillaries located in the normal human utricular stroma showed vascular endothelial cells with few pinocytotic vesicles, covered by a smooth and uniform basement membrane surrounded by pericyte processes. Meniere’s disease specimens revealed differential ultrastructural pathological changes in the cellular elements of the microvasculature. With moderate degeneration of the BLB, there were numerous vesicles within the vascular endothelial cells (VECs), with increased numbers at the abluminal face, pericyte process detachment and disruption of the perivascular basement membrane surrounding the VECs. With severe degeneration of the BLB, there was severe vacuolization or frank apparent necrosis of VECs and loss of subcellular organelles. A higher severity of BLB degenerative changes was associated with a higher degree of basement membrane thickening and edematous changes within the vestibular stroma. This study presents the first ultrastructural analysis of the capillaries constituting the BLB in the human vestibular macula utricle from normal and Meniere’s disease.

Assessment of Vestibulo-oculomotor Reflex in Ménière's Disease: Defining an Instrumental Profile

OBJECTIVES

To analyze and compare, in two groups of patients affected by definite Ménière's disease (MD) but treated differently, the Video Head Impulse Test findings especially by putting them in relationship with canal paresis, hearing loss, and duration of the disease.

STUDY DESIGN

Retrospective chart review.

PATIENTS

Seventy patients affected by unilateral definite MD (16 in Group 1 and 54 in Group 2) observed between March 2014 and May 2015 in a tertiary referral center were retrospectively studied and then divided into two groups: Group 1 was previously treated with intratympanic gentamicin, whereas Group 2 underwent only a conservative therapy. Instrumental tests included audiometry, caloric test, and Video Head Impulse Test. All the findings were statistically analyzed; significance was set at p = 0.005.

INTERVENTION

Diagnostic.

MAIN OUTCOMES MEASURES

If MD is treated conservatively the high-frequency vestibulo-oculomotor reflex gain determined with Video Head Impulse Test is normal; it is pathological if MD is treated with gentamicin.

RESULTS

High-frequency vestibulo-oculomotor reflex gain showed a statistically significant reduction in Group 1; at the same time, it showed no correlation in both groups with hearing loss, duration of disease or canal paresis.

CONCLUSION

High-frequency vestibulo-oculomotor reflex is naturally preserved even in late stage MD if the patient has been treated conservatively; the dissociation between Caloric Test and Video Head Impulse Test findings could be considered an instrumental hallmark of MD. Gentamicin significantly reduces high-frequency vestibulo-oculomotor reflex gain: this reduction can be taken into account when determining the effectiveness of an ablative treatment.

Immunohistochemical techniques for the human inner ear

In this review, we provide a description of the recent methods used for immunohistochemical staining of the human inner ear using formalin-fixed frozen, paraffin and celloidin-embedded sections. We also show the application of these immunohistochemical methods in auditory and vestibular endorgans microdissected from the human temporal bone. We compare the advantages and disadvantages of immunohistochemistry (IHC) in the different types of embedding media. IHC in frozen and paraffin-embedded sections yields a robust immunoreactive signal. Both frozen and paraffin sections would be the best alternative in the case where celloidin-embedding technique is not available. IHC in whole endorgans yields excellent results and can be used when desiring to detect regional variations of protein expression in the sensory epithelia. One advantage of microdissection is that the tissue is processed immediately and IHC can be made within 1 week of temporal bone collection. A second advantage of microdissection is the excellent preservation of both morphology and antigenicity. Using celloidin-embedded inner ear sections, we were able to detect several antigens by IHC and immunofluorescence using antigen retrieval methods. These techniques, previously applied only in animal models, allow for the study of numerous important proteins expressed in the human temporal bone potentially opening up a new field for future human inner ear research.

Comparison of caloric and head-impulse tests during the attacks of Meniere's disease

OBJECTIVES/HYPOTHESIS

To aid in diagnosis of Meniere's disease (MD) during the attacks using caloric and head-impulse tests (HITs).

STUDY DESIGN

Retrospective case series review.

METHODS

We analyzed the results of bithermal caloric and HITs during the attacks in 16 patients with MD. Quantitative analyses of HITs were conducted using a magnetic search coil technique.

RESULTS

In unilateral MD (14 patients, 42 semicircular canals), the head impulse gain of the vestibulo-ocular reflex (VOR) was either normal (28 of 42, 67%), decreased (8 of 42, 19%), or increased (6 of 42, 14%) for each semicircular canal in the affected ear. Likewise, the head impulse VOR gain was either normal (29 of 42, 69%), increased (11 of 42, 26%), or decreased (2 of 42, 5%) in the intact ear. The VOR gain for the horizontal canal was significantly lower on the affected side (P = 0.013). However, the VOR gains for the anterior and posterior canals did not differ between the sides (P = 0.270, P = 0.282). In bilateral MD (two patients, 12 semicircular canals), the VOR gain was either decreased (6 of 12, 50%) or normal (6 of 12, 50%) in either ear. In contrast, the caloric responses were usually decreased in the affected ear (7 of 11, 64%, including one with bilateral MD).

CONCLUSION

During the attacks of MD, HITs showed varied results between the ears and among the canals, although the caloric responses were usually decreased in the involved ear. These dissociations suggest a frequency-dependent impairment of canal function or mechanical property of the endolymphatic hydrops during the attacks of MD.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:702-708, 2017.

What does the dissociation between the results of video head impulse versus caloric testing reveal about the vestibular dysfunction in Ménière's disease?

CONCLUSION

It is suggested that the different results of rotational (video head impulse - vHIT) and caloric tests in patients with Ménière's disease (MD) may be a consequence of the physical enlargement of the membranous duct in the hydropic labyrinths in MD, causing a reduced response to caloric stimulation.

OBJECTIVES

There have been reports that the results of two tests of semicircular canal function, the caloric response and the responses to vHIT do not agree. This retrospective study at a tertiary referral hospital examined this disagreement.

METHODS

This study reviewed the data of 22 patients who met the AAO-HNS criteria for MD and who had both caloric and vHIT testing.

RESULTS

There was a clear dissociation: patients with MD had a small or absent response to caloric stimulation of their affected ear, whilst their response to vHIT was in the normal range.

DISCUSSION

The accepted Gentine model of the mechanism of caloric stimulation could account for this dissociation: the increased diameter of the semicircular duct in hydropic labyrinths resulting in endolymph circulation within the duct itself and so a smaller thermally induced pressure across the cupula. The increased duct diameter will have little effect on responses to rotation.

What does the head impulse test versus caloric dissociation reveal about vestibular dysfunction in Ménière's disease?

In patients with Ménière's disease (MD), caloric testing can show, depending on the stage and activity of the disease, a variety of results. Between attacks, many, or perhaps even most, patients with unilateral early or mild MD have normal caloric tests; late MD can show abnormalities ranging from mild to severe unilateral canal paresis with or without directional preponderance. The explanation of canal paresis in MD is not clear. The most obvious explanation, severe loss of lateral canal hair cells, is not likely to be correct because hair cell loss will not explain the fluctuating canal paresis to caloric stimulation. In contrast, the published evidence is that rotational testing of semicircular canal function in MD patients typically shows little reduction in function and even enhancement of vestibulo-ocular reflex gain, at least in the early stages of the disease. Here, we offer a novel explanation for this dissociation. We propose that hydropic expansion of the lateral canal membranous labyrinth permits convective recirculation within the duct that allows dissipation of the hydrostatic force that would normally cause cupular displacement and nystagmus in the caloric test.

Vestibular implantation and longitudinal electrical stimulation of the semicircular canal afferents in human subjects

Animal experiments and limited data in humans suggest that electrical stimulation of the vestibular end organs could be used to treat loss of vestibular function. In this paper we demonstrate that canal-specific two-dimensionally (2D) measured eye velocities are elicited from intermittent brief 2 s biphasic pulse electrical stimulation in four human subjects implanted with a vestibular prosthesis. The 2D measured direction of the slow phase eye movements changed with the canal stimulated. Increasing pulse current over a 0-400 μA range typically produced a monotonic increase in slow phase eye velocity. The responses decremented or in some cases fluctuated over time in most implanted canals but could be partially restored by changing the return path of the stimulation current. Implantation of the device in Meniere's patients produced hearing and vestibular loss in the implanted ear. Electrical stimulation was well tolerated, producing no sensation of pain, nausea, or auditory percept with stimulation that elicited robust eye movements. There were changes in slow phase eye velocity with current and over time, and changes in electrically evoked compound action potentials produced by stimulation and recorded with the implanted device. Perceived rotation in subjects was consistent with the slow phase eye movements in direction and scaled with stimulation current in magnitude. These results suggest that electrical stimulation of the vestibular end organ in human subjects provided controlled vestibular inputs over time, but in Meniere's patients this apparently came at the cost of hearing and vestibular function in the implanted ear.

The vestibulo-ocular reflex assessment in patients with Ménière's disease: examining all semicircular canals

Abstract Conclusion: The distribution of abnormal results is not uniform between different canals in each patient; the most frequent gain reduction is obtained for the posterior canal. Gain reduction reflects the disease duration and amount of hearing loss.

OBJECTIVE

To test the hypothesis that the vestibulo-ocular reflex (VOR) evoked after stimulation of each semicircular canal behaves in a different manner in patients with unilateral definite Ménière's disease.

METHODS

We studied the VOR evoked by rapid head-impulses in the plane of the 6 semicircular canals in 36 patients. It was evaluated with a video system that analyzes the head and eye velocity and the gain was the objective measure.

RESULTS

In 12 (33.3%) patients the examination of both ears was normal for all the semicircular canals, in 12 patients the results from the affected ear were abnormal in at least 1 of the semicircular canals, in 11 (30.5%) patients the results were abnormal in at least 1 of the semicircular canals in both the affected and unaffected ears, and in 1 (2.9%) patient the results were abnormal only in the unaffected ear. The most frequent abnormal result was obtained from the posterior canal of the affected ear and from the coupled superior canal of the unaffected ear. The distribution of abnormal findings was dependent on the disease duration and hearing loss.

Hyaluronan up-regulation is linked to renal dysfunction and hearing loss induced by silver nanoparticles

Increased application of silver nanoparticles (AgNPs) has raised concerns on their potential adverse effects on human health. However, the precise toxicological mechanisms are not known in detail. The current study hypothesized that AgNPs induced glycosaminoglycan accumulation in the basement membrane that associated with the up-regulation of its component hyaluronic acid, known as a hydrophilic molecule of binding and retaining water, and caused toxicities in the kidney and cochlea. Rats administered AgNPs through either intravenous or intratympanic injection were observed at different time points after exposure. The concentrations of creatinine and urea in the serum were elevated remarkably, and proteins leaked into the urine were increased. A significant hearing loss over a broad range of frequencies was indicated. AgNP exposure induced glycosaminoglycan accumulation and hyaluronic acid up-regulation in the basement membrane. Abundant apoptotic cell death was demonstrated in the AgNP-exposed organs. Our results suggested that glycosaminoglycan accumulation associated with the up-regulation of hyaluronic acid was involved in the toxicities of kidney and cochlea caused by AgNPs.

Cochlin expression in vestibular endorgans obtained from patients with Meniere's disease

The distribution of cochlin and its associated basement membrane proteins (collagen IV, collagen II, laminin-β2, and nidogen-1) were evaluated in the vestibular endorgans of subjects with Meniere's disease and compared with normal specimens. Cochlin mRNA expression in vestibular endorgans from Meniere's disease specimens was also investigated. Specimens were obtained from patients who had Meniere's disease and who were undergoing ablative labyrinthectomy. Control specimens were obtained both from autopsy specimens with documented normal audiovestibular function and from patients undergoing labyrinthectomy for acoustic neuroma excision. In the normal control specimens, cochlin immunoreactivity was found evenly distributed in the stroma of the cristae ampullaris and maculae of the utricle. In Meniere's specimens, cochlin immunoreactivity was markedly increased; this was associated with an increase in cochlin mRNA expression as shown by real-time reverse transcription with the polymerase chain reaction. Collagen IV and laminin-β2 immunoreactivity was significantly decreased in Meniere's specimens. Nidogen-1 and collagen II immunoreactivity was unchanged in Meniere's specimens when compared with normal samples. Cochlin upregulation has been implicated in the hereditary audiovestibulopathy, DFNA9. The increased expression of cochlin and decreased expression of collagen IV and laminin in Meniere's disease are suggestive that the overexpression of cochlin contributes to the dysfunctional inner ear homeostasis seen in this disease.

The modified ampullar approach for vestibular implant surgery: feasibility and its first application in a human with a long-term vestibular loss

Objective: To assess, for the first time in a human with a long-term vestibular loss, a modified approach to the ampullae and the feasibility of evoking a VOR by ampullar stimulation. Materials and methods: Peroperative stimulation of the ampullae, using the ampullar approach, was performed under full anesthesia during cochlear implantation in a 21-year-old female patient, who had experienced bilateral vestibular areflexia and sensorineural hearing loss for almost 20 years. Results: The modified ampullar approach was performed successfully with as minimally invasive surgery as possible. Ampullar stimulation evoked eye movements containing vectors congruent with the stimulated canal. As expected, the preliminary electrophysiological data were influenced by the general anesthesia, which resulted in current spread and reduced maximum amplitudes of eye movement. Nevertheless, they confirm the feasibility of ampullar stimulation. Conclusion: The modified ampullar approach provides safe access to the ampullae using as minimally invasive surgery as possible. For the first time in a human with long-term bilateral vestibular areflexia, it is shown that the VOR can be evoked by ampullar stimulation, even when there has been no vestibular function for almost 20 years. This approach should be considered in vestibular surgery, as it provides safe access to one of the most favorable stimulus locations for development of a vestibular implant.

Meniere's disease might be an autoimmune condition?

OBJECTIVES

To review our current knowledge of the pathogenesis of Meniere's disease, including viral infection and immune system-mediated mechanisms, and to discuss the pathogenesis as it relates to pharmacotherapy.

SYSTEMATIC REVIEW METHODOLOGY

Relevant publications on the aetiopathogenesis, molecular biology, genetics and histopathology of Meniere's disease from 1861 to 2011 were analysed.

RESULTS AND CONCLUSIONS

Meniere's disease is characterised by intermittent episodes of vertigo, fluctuating sensorineural hearing loss, tinnitus, and aural pressure. The aetiology and pathogenesis remain unknown. Proposed theories of causation include viral infections and immune system-mediated mechanisms. The immune response in Meniere's disease is focused on inner ear antigens. Approximately one-third of Meniere's disease cases seem to be of an autoimmune origin although the immunological mechanisms involved are not clear. The diagnosis of autoimmune inner ear disease is based either on clinical criteria or on a positive response to steroids. The antiviral approach has virtually eliminated the use of various surgical methods used in the past. Steroid responsiveness is high, and with prompt treatment, inner ear damage may be reversible. The administration of etanercept improves or stabilises symptoms in treated patients. Treatment of antiphospholipid syndrome can be directed toward preventing thromboembolic events by using antithrombotic medications. Only warfarin has been shown to be effective. Gene therapy can be used to transfer genetic material into inner ear cells using viral vectors and to protect, rescue, and even regenerate hair cells of the inner ear.

The vestibular implant: quo vadis?

Objective: To assess the progress of the development of the vestibular implant (VI) and its feasibility short-term. Data sources: A search was performed in Pubmed, Medline, and Embase. Key words used were “vestibular prosth*” and “VI.” The only search limit was language: English or Dutch. Additional sources were medical books, conference lectures and our personal experience with per-operative vestibular stimulation in patients selected for cochlear implantation. Study selection: All studies about the VI and related topics were included and evaluated by two reviewers. No study was excluded since every study investigated different aspects of the VI. Data extraction and synthesis: Data was extracted by the first author from selected reports, supplemented by additional information, medical books conference lectures. Since each study had its own point of interest with its own outcomes, it was not possible to compare data of different studies. Conclusion: To use a basic VI in humans seems feasible in the very near future. Investigations show that electric stimulation of the canal nerves induces a nystagmus which corresponds to the plane of the canal which is innervated by the stimulated nerve branch. The brain is able to adapt to a higher baseline stimulation, while still reacting on a dynamic component. The best response will be achieved by a combination of the optimal stimulus (stimulus profile, stimulus location, precompensation), complemented by central vestibular adaptation. The degree of response will probably vary between individuals, depending on pathology and their ability to adapt.

Immunocytochemical distribution of WARP (von Willebrand A domain-related protein) in the inner ear

The basic components of the epithelial, perineural, and perivascular basement membranes in the inner ear have been well-documented in several animal models and in the human inner ear. The von Willebrand A domain-related protein (WARP) is an extracellular matrix molecule with restricted expression in cartilage, and a subset of basement membranes in peripheral nerves, muscle, and central nervous system vasculature. It has been suggested that WARP has an important role in maintaining the blood-brain barrier. To date no studies on WARP distribution have been performed in the inner ear, which is equipped with an intricate vasculature network. In the present study, we determined the distribution of WARP by immunocytochemistry in the human inner ear using auditory and vestibular endorgans microdissected from human temporal bones obtained at autopsy. All subjects (n=5, aged 55-87years old) had documented normal auditory and vestibular function. We also determined the WARP immunolocalization in the mouse inner ear. WARP immunoreactivity localized to the vasculature throughout the stroma of the cristae ampullaris, the maculae utricle, and saccule in the human and mouse. In the human and mouse inner ear, WARP immunoreactivity delineated blood vessels located in the stria vascularis, spiral ligament, sub-basilar region, stromal tissue, and the spiral and vestibular ganglia. The distinct localization of WARP in the inner ear vasculature suggests an important role in maintaining its integrity. In addition, WARP allows delineation of microvessels in the inner ear allowing the study of vascular pathology in the development of otological diseases.

Immunohistochemical localization and mRNA expression of aquaporins in the macula utriculi of patients with Meniere's disease and acoustic neuroma

Meniere's disease is nearly invariably associated with endolymphatic hydrops (the net accumulation of water in the inner ear endolymphatic space). Vestibular maculae utriculi were acquired from patients undergoing surgery for Meniere's disease and acoustic neuroma and from autopsy (subjects with normal hearing and balance). Quantitative immunostaining was conducted with antibodies against aquaporins (AQPs) 1, 4, and 6, Na(+)K(+)ATPase, Na(+)K(+)2Cl co-transporter (NKCC1), and alpha-syntrophin. mRNA was extracted from the surgically acquired utricles from subjects with Meniere's disease and acoustic neuroma to conduct quantitative real-time reverse transcription with polymerase chain reaction for AQP1, AQP4, and AQP6. AQP1 immunoreactivity (-IR) was located in blood vessels and fibrocytes in the underlying stroma, without any apparent alteration in Meniere's specimens when compared with acoustic neuroma and autopsy specimens. AQP4-IR localized to the epithelial basolateral supporting cells in Meniere's disease, acoustic neuroma, and autopsy. In specimens from subjects with Meniere's disease, AQP4-IR was significantly decreased compared with autopsy and acoustic neuroma specimens. AQP6-IR occurred in the sub-apical vestibular supporting cells in acoustic neuroma and autopsy samples. However, in Meniere's disease specimens, AQP6-IR was significantly increased and diffusely redistributed throughout the supporting cell cytoplasm. Na(+)K(+)ATPase, NKCC1, and alpha-syntrophin were expressed within sensory epithelia and were unaltered in Meniere's disease specimens. Expression of AQP1, AQP4, or AQP6 mRNA did not differ in vestibular endorgans from patients with Meniere's disease. Changes in AQP4 (decreased) and AQP6 (increased) expression in Meniere's disease specimens suggest that the supporting cell might be a cellular target.