Symptomatic versus asymptomatic endolymphatic hydrops: a histopathologic comparison

Potential Application of Hydrops MR Imaging: A Systematic Review

BACKGROUND

Diagnostic dilemma between clinical Meniere's disease and radiological endolymphatic hydrops (EH) has emerged since the introduction of hydrops magnetic resonance imaging (MRI). The aim of this study is to explore the potential application of hydrops MRI on diagnosing the EH.

METHODS

This review was developed from peer-reviewed articles published in those journals listed on journal of citation reports. The MEDLINE database of the US National Library of Medicine, Scopus, and Google Scholar were used to collect articles based on the guidelines (PRISMA 2020 statement) for reporting reviews.

RESULTS

Initially, 470 articles were retrieved from 1983 to 2023, and 80 relevant articles were ultimately selected. The sensitivity (69%-92%) and specificity (78%-96%) values varied from each laboratory for detecting EH via hydrops MRI, probably due to candidate selection and the grading system employed.

CONCLUSION

The application of hydrops MRI allows (1) differentiation between EH and sudden sensorineural hearing loss; (2) determination of the affected side of EH; and (3) confirmation of the diagnosis of EH concomitant with other disorders. Notably, not all differentials for EH can be visualized on MR images. One of the existing gaps to be filled is that updated hydrops MRI fails to identify distortion, that is, rupture, collapse, fistula, or fibrosis of the inner ear compartments, akin to what histopathological evidence can demonstrate. Hence, enhanced ultrahigh resolution of hydrops MRI is required for demonstrating fine structures of the inner ear compartments in the future.

The role of serum osmolality in Meniere's disease with acute sensorineural hearing loss

OBJECTIVE

This study investigated the role of serum osmolality in Meniere's disease (MD) patients with acute sensorineural hearing loss (SNHL).

DESIGN

Retrospective study.

STUDY SAMPLES

Twenty definite MD patients with acute unilateral SNHL were treated with an osmotic diuretic (Isosorbide, 100 mL daily) and assigned to Group A. Another 20 age- and sex-matched definite MD patients with acute SNHL were not given Isosorbide and assigned to Group B. Both groups underwent audiometry and blood examination for serum osmolality before and after treatment.

RESULTS

Group A revealed a significant increase in serum osmolality after treatment. The optimal cut-off values for increased serum osmolality in Group A were +1.5 mOSM/L for predicting hearing improvement at frequencies of 250-1000 Hz, and +2.5 mOSM/L at 2000-4000 Hz. Comparing increased levels of serum osmolality (> +2.0 vs. ≤ +2.0 mOSM/L), Isosorbide dosing at 3.0 L vs. 1.0 L, significantly differed in the odds ratio (OR). Isosorbide at a total dosage of 3.0 L thus improves the hearing threshold by >10 dB at frequencies of 250-2000 Hz.

CONCLUSION

The Isosorbide at a total dosage of 3.0 L may increase serum osmolality by > +2.0 mOSM/L, and improve the hearing threshold for hydropic ears at least >10 dB at low- and mid-frequencies.

In Silico Localization of Perilymph Proteins Enriched in Meńier̀e Disease Using Mammalian Cochlear Single-cell Transcriptomics

Hypothesis

Proteins enriched in the perilymph proteome of Meńier̀e disease (MD) patients may identify affected cell types. Utilizing single-cell transcriptome datasets from the mammalian cochlea, we hypothesize that these enriched perilymph proteins can be localized to specific cochlear cell types.

Background

The limited understanding of human inner ear pathologies and their associated biomolecular variations hinder efforts to develop disease-specific diagnostics and therapeutics. Perilymph sampling and analysis is now enabling further characterization of the cochlear microenvironment. Recently, enriched inner ear protein expression has been demonstrated in patients with MD compared to patients with other inner ear diseases. Localizing expression of these proteins to cochlear cell types can further our knowledge of potential disease pathways and subsequent development of targeted therapeutics.

Methods

We compiled previously published data regarding differential perilymph proteome profiles amongst patients with MD, otosclerosis, enlarged vestibular aqueduct, sudden hearing loss, and hearing loss of undefined etiology (controls). Enriched proteins in MD were cross-referenced against published single-cell/single-nucleus RNA-sequencing datasets to localize gene expression to specific cochlear cell types.

Results

In silico analysis of single-cell transcriptomic datasets demonstrates enrichment of a unique group of perilymph proteins associated with MD in a variety of intracochlear cells, and some exogeneous hematologic and immune effector cells. This suggests that these cell types may play an important role in the pathology associated with late MD, suggesting potential future areas of investigation for MD pathophysiology and treatment.

Conclusions

Perilymph proteins enriched in MD are expressed by specific cochlear cell types based on in silico localization, potentially facilitating development of disease-specific diagnostic markers and therapeutics.

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.

A Historical Perspective on Surgical Manipulation of the Membranous Labyrinth for Treatment of Meniere's Disease

Meniere's disease is an inner ear disorder without a known cause. Endolymphatic hydrops is a swelling of the endolymph spaces that has been observed consistently on post-mortem histology in patients with a history of Meniere's disease but can occur in asymptomatic individuals and in association with other diseases. Since its discovery, Meniere's disease has been a disorder managed primarily by otolaryngologists. Surgical treatments, therefore, have accompanied attempts at medical management. Inspired by patients' sensations of ear fullness and later by the histologic findings of hydrops, surgeons began manipulating the membranous labyrinth to relieve episodes of vertigo while attempting to preserve hearing. This review highlights this history of manipulation of the membranous labyrinth. These procedures indicate a rich history of innovation that parallels developments in otologic surgery. The studies involving patients are uniformly retrospective, with some procedures performed first in animal models of endolymphatic hydrops. Many approaches were endorsed by eminent otologic surgeons. Surgeries on the endolymphatic sac are performed by some surgeons today; however, procedures on the membranous labyrinth resulted in similar symptomatic relief through a minimally invasive technique, in many cases performed using only local anesthetic. Episodic vertigo in patients with Meniere's disease is a distressing symptom, yet spontaneous remissions are common. The reports of procedures on the membranous labyrinth reviewed here consistently indicated fewer vertigo episodes. Variable degrees of hearing loss were common following these procedures, and many were abandoned. Additional innovative surgeries are inevitable, but we must understand better the relationships among endolymphatic hydrops, Meniere's disease pathophysiology, and patient symptoms.

Isolated Saccular Hydrops on High-resolution MRI Is Associated With Full Spectrum Menière's Disease

OBJECTIVE

To describe the clinical presentation of patients with isolated saccular endolymphathic hydrops (EH) detected.

STUDY DESIGN

Clinical case series.

SETTING

University-based tertiary referral center.

PATIENTS

All subjects presenting with vertigo or hearing loss who had isolated saccular EH detected.

INTERVENTION

High-resolution delayed-contrast magnetic resonance imaging (MRI) conducted between November 2015 and November 2016.

MAIN OUTCOME MEASURES

Audiovestibular testing results and analysis of clinical histories.

RESULTS

Isolated saccular EH was detected in 18 subjects. Sixteen met criteria for definite Menière's disease (MD, n = 12) or delayed endolymphatic hydrops (DEH, n = 4). One had a history of sudden sensorineural hearing loss (SSNHL) and 3 years after MRI developed recurrent vertigo characteristic of DEH. One patient had a history of atypical DEH (Tumarkin falls without vertigo following SSNHL). Four patients had Tumarkin falls. Most (83%) demonstrated mild-to-severe low-frequency fluctuating loss, and six (33.3%) had a history of ipsilateral sudden profound SNHL. Nine of the 17 (53%) patients tested had an ipsilateral caloric paresis ranging from 26 to 67%. Ipsilateral vestibular-evoked myogenic potentials showed reduced or absent responses in 5 of the 17 tested (29%).

CONCLUSIONS

The full spectrum of MD may be associated with saccular hydrops. We propose that MD and DEH often begin in the saccule, and MRI may provide clues to the pathophysiology of MD. Saccular hydrops was present in one patient with SSNHL who did not develop vertigo spells until 3 years after MRI, indicating that saccular hydrops may be the first manifestation of MD or DEH.

Evidence of Large Vestibulo-Ocular Reflex Reduction in Patients With Menière Attacks

OBJECTIVE

To examine the high frequency horizontal vestibular ocular-reflex (hVOR) during acute attacks of vertigo in Menière's disease (MD).

STUDY DESIGN

Retrospective case series and literature review.

SETTING

Tertiary academic medical center.

PATIENTS

Patients with clinical diagnosis of unilateral "definite MD."

INTERVENTION

Review of medical records.

MAIN OUTCOME MEASURES

Spontaneous nystagmus and the dynamic hVOR gain change at different stages of an acute episode of MD attack.

RESULTS

We studied 10 vertigo attacks during the unique stages of the episode. During the acme stage of the attack, lower hVOR gain was recorded on the affected side (mean 0.48 ± 0.23), which was associated with a paralytic nystagmus (beating away from the affected ear). Additionally, the mean hVOR gain remained significantly (p < 0.05) reduced during each of the other stages of the attack as compared with the unaffected side and a control group. After the attack, mean hVOR gains normalized in the affected ear. Mean hVOR gain of the unaffected ear remained normal during all stages.

CONCLUSION

Vestibular function during an attack of MD is a dynamic process associated with fluctuation of the dynamic (hVOR gain) and static (spontaneous nystagmus) processes, which exist in parallel with the perception of vertigo. Our data support vHIT monitoring during an episode to provide objective and accurate evidence of the ear with active disease. This would be particularly useful for those patients with MD presentations of unreliable hearing or assisting to identify the ear to be treated in the case of bilateral MD.

Which is the optimally defined vestibular cross-section to diagnose unilateral Meniere's disease with delayed post-gadolinium 3D fluid-attenuated inversion recovery MRI?

OBJECTIVES

Delayed post-gadolinium 3D fluid-attenuated inversion recovery (FLAIR) MRI is used to support a diagnosis of Ménière's disease (MD) with the ratio of the endolymphatic space (ES) to the sum of the endolymphatic and perilymphatic spaces (SEPS) on a cross-section through the vestibule being a key diagnostic criterion. It was hypothesised that the exact definition of the vestibular cross-section would influence the ES: SEPS ratio, its ability to diagnose MD, and its reproducibility.

METHODS

Following institutional approval, 22 patients (five male, 17 female; mean age 52.1) with unilateral MD and delayed post-gadolinium 3D FLAIR MRI were retrospectively analysed. Two observers measured the ES and SEPS on predefined axial (superior and inferior) and sagittal vestibular cross-sections. Receiver operating characteristic (ROC) curves, Bland-Altman plots and intraclass correlation (ICC) were analysed for the ES:SEPS ratios.

RESULTS

The area under the curve (AUC) was decreased for the ES:SEPS ratios on the superior axial section through the vestibule (AUC 0.737) compared to the inferior axial (AUC 0.874) and sagittal sections (AUC 0.878). The resulting optimal thresholds (sensitivities/specificities) were 0.21 (0.66/0.75), 0.16 (0.77/0.9) and 0.285 (0.75/0.96). The reproducibility was excellent for all measures with ICCs of 0.97, 0.98 and 0.99.

CONCLUSION

Inferior axial or sagittal vestibular cross-sections are more accurate for the diagnosis of MD ears and have excellent reproducibility.

ADVANCES IN KNOWLEDGE

The choice of vestibular cross-section influences both the ability to distinguish MD from asymptomatic contralateral ears, and the optimum threshold ES:SEPS value.

Chronic cerebrospinal venous insufficiency and menière's disease: Interventional versus medical therapy

OBJECTIVES/HYPOTHESIS

To evaluate the incidence of chronic cerebrospinal venous insufficiency in Menière's disease patients and the effect of bilateral percutaneous transluminal angioplasty of the jugular/azygos veins compared to medical therapy.

STUDY DESIGN

Prospective case-control study.

METHODS

Five hundred fourteen subjects were included in the study, 412 affected by definite Menière's disease, and 102 healthy controls. All patients underwent audiovestibular and vascular examination. Patients with Menière's disease and concomitant cerebrospinal venous insufficiency were divided in two subgroups: patients who underwent vascular intervention with bilateral percutaneous transluminal angioplasty (PTA) of the jugular/azygos veins and patients treated with medical therapy.

RESULTS

Chronic cerebrospinal venous insufficiency was diagnosed in 330/412 (80.1%) Menière's disease patients and in 12/102 healthy individuals (11.8%) (P < .001). In the two chronic cerebrospinal venous insufficiency subgroups, a significant difference in Dizziness Handicap Inventory scores was found between patients in the PTA group compared to patients treated with medical therapy (31 ± 8.6 vs. 48.1 ± 14.4; P < .001); no significant differences were found for the Tinnitus Handicap Inventory scores (50.8 ± 16.58 vs. 49.6 ± 17.5; P = .23). Subjective evaluation of aural fullness was significantly better in patients in the PTA group (P = .003) as well as pure-tone average, which was significantly different between groups (49.8 ± 16.5 dB in the PTA group vs. 55.8 ± 13 in the medical therapy group; P = .035).

CONCLUSIONS

The results of the present study confirm the close relationship between vascular disorders and Menière's disease. The encouraging responses to vascular interventional therapy on Meniére's disease symptoms suggest that this may be a promising path for interpretation and treatment of this complex disease.

LEVEL OF EVIDENCE

2b Laryngoscope, 130: 2040-2046, 2020.

Recent and Frequent Vertigo Attacks Produce Negative Findings on Furosemide-Loading Vestibular Evoked Myogenic Potential Testing in Meniere's Disease

Objective: The peak-to-peak amplitude of the p13-n23 wave in cervical vestibular evoked myogenic potential can increase after furosemide administration in patients with Meniere's disease [furosemide-loading VEMP (FVEMP) testing]. The examination is used to test for the presence of endolymphatic hydrops; we investigated factors that may influence the results.

Methods: Forty-two subjects (23 males and 19 females, aged 24–70 years) with unilateral definite Meniere's disease who underwent FVEMP testing were retrospectively studied. Possible factors associated with the results of FVEMP testing were studied using logistic regression analysis.

Results: Ages, sex, affected side, stage, disease duration, and mean hearing level of pure tone audiometry did not influence the results of FVEMP testing in the univariate analysis (p > 0.05). Number of days since the last vertigo attack [odds ratio (OR): 1.07, p = 0.031] and frequency of vertigo attacks per month (OR: 0.42, p = 0.003) were significantly associated with the results of testing. Multivariate analysis showed that both days since the last vertigo attack < 7 (OR: 0.13, p = 0.04) and frequency of vertigo attacks per month ≥ 2 (OR: 0.06, p = 0.004) were risk factors for negative results on FVEMP testing.

Conclusion: This study found that recent and frequent vertigo attacks produced negative findings on FVEMP testing in Meniere's disease. This apparently irrational finding can be explained by the consequences of membranous labyrinth rupture during vertigo attacks, where the altered saccular resonance due to EH cannot be recovered by furosemide administration because of the dissolving dehydration effect that occurs through communication between the endolymphatic and perilymphatic spaces. In addition, the impairment of sensory cells that is caused by endolymph and perilymph mixing upon rupture does not improve upon furosemide administration. FVEMP testing results may provide us with pathophysiological information regarding the membranous labyrinth.

The Progressive Nature of Menière's Disease: Stress Projections and Lesion Analysis

HYPOTHESIS

An engineering model of the labyrinth can provide a mechanism that accounts for the pattern of lesion development observed in Menière's disease.

BACKGROUND

Membrane lesions in Menière's disease can occur in virtually every part of the membranous labyrinth. How these lesions are induced is unclear and their mode of distribution uncertain. Pressure induced stress in the membranous labyrinth may play a mechanistic role in lesion formation and distribution.

METHODS

An engineering model of the labyrinth was used to provide membrane stress formulations and projections for lesion induction in the several chambers using membrane theory. These were compared with an analysis of actual lesions observed in Menière's disease to evaluate the model's accuracy.

RESULTS

The model projects that lesions in the membranous labyrinth will be induced progressively because of stress differentials among the chambers, with a chain of lesion pattern that follows the serial anatomic order and occurs with a frequency commensurate with chamber stress level. An analysis of lesions observed in actual cases of Menière's disease reveals a pattern of lesion development that is progressive, sequential, commensurate, and concordant with the model's stress projections.

CONCLUSIONS

The concordance between the stress projections and the lesion analysis strengthens the hypothesis that Menière's is a progressive disease that follows a chain of lesions paradigm based on pressure-induced stress differentials in the variously configured chambers of the membranous labyrinth.

A three-dimensional analysis of the endolymph drainage system in Ménière disease

OBJECTIVES/HYPOTHESIS

To measure the volume of the endolymph drainage system in temporal bone specimens with Ménière disease, as compared with specimens with endolymphatic hydrops without vestibular symptoms and with nondiseased specimens STUDY DESIGN: Comparative human temporal bone analysis.

METHODS

We generated three-dimensional models of the vestibular aqueduct, endolymphatic sinus and duct, and intratemporal portion of the endolymphatic sac and calculated the volume of those structures. We also measured the internal and external aperture of the vestibular aqueduct, as well as the opening (if present) of the utriculoendolymphatic (Bast's) valve and compared the measurements in our three study groups.

RESULTS

The volume of the vestibular aqueduct and of the endolymphatic sinus, duct, and intratemporal endolymphatic sac was significantly lower in the Ménière disease group than in the endolymphatic hydrops group (P <.05). The external aperture of the vestibular aqueduct was also smaller in the Ménière disease group. Bast's valve was open only in some specimens in the Ménière disease group.

CONCLUSIONS

In temporal bones with Ménière disease, the volume of the vestibular aqueduct, endolymphatic duct, and intratemporal endolymphatic sac was lower, and the external aperture of the vestibular aqueduct was smaller as compared with bones from donors who had endolymphatic hydrops without vestibular symptoms and with nondiseased bones. The open status of the Bast's valve in the Ménière disease group could be secondary to higher retrograde endolymph pressures caused by smaller drainage systems. These anatomic findings could correlate with the reason that some patients with hydrops develop clinical symptoms, whereas others do not.

LEVEL OF EVIDENCE

N/A Laryngoscope, 127:E170-E175, 2017.

In Vivo Visualization of Endolymphatic Hydrops in Guinea Pigs: Magnetic Resonance Imaging Evaluation at 4.7 Tesla

In order to find out whether it is possible to visualize experimental endolymphatic hydrops in the cochlea with magnetic resonance imaging (MRI) at 4.7 T, we used 11 guinea pigs. Five normal guinea pigs were used as controls. Early manifestation of endolymphatic hydrops was evaluated in endolymphatic sac (ES)-intact animals (n = 6), and advanced manifestation in ES-damaged animals (n = 5) by means of MRI with gadolinium-diethylenetriaminepentaacetate-bismethylamide (Gd-DTPA-BMA) contrast agent. Hearing was tested with electrocochleography. The surface area of 3 partitions of the cochlea was used to quantify endolymphatic hydrops. The fine structure of the 3 partitions of the cochlea was visualized with MRI in all animals, as Gd-DTPA-BMA appeared mainly in the scala tympani and scala vestibuli. As early as 5 days after endolymphatic sac surgery, endolymphatic hydrops started to appear as visualized by MRI and also verified with histology. Severe damage to the inner ear barrier with Gd-DTPA-BMA leakage into the scala media was detected with MRI in 1 ES-damaged animal that had a 60-dB hearing loss. To conclude, endolymphatic hydrops can be visualized with high-resolution MRI by means of Gd-DTPA-BMA, and it is possible to quantify the extent of endolymphatic hydrops. Damage to the inner ear barrier or possible rupture of membranes can be shown with the assistance of Gd-DTPA-BMA.

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.

Membrane Stress in the Human Labyrinth and Meniere Disease: A Model Analysis

Introduction The nature and extent of membrane damage encountered in Meniere disease remains unexplained. Pressure-induced membrane stress may underlie the characteristic hydropic distention. Analysis of stress in the several vestibular chambers may offer insight into the nature and progression of Meniere disease. Objective Membrane stress levels will be assessed by constructing a specific model of the human membranous labyrinth through the application of human dimensions to an existing generic model of the mammalian labyrinth. Methods Nominal dimensions for a model of the human membranous labyrinth were obtained from fixed human tissue. Stress proclivities were calculated and normalized based on shell theory applied to the various geometric figures comprising the model. Results Normalized peak stress levels were projected to be highest in the saccule (38.8), followed by the utricle (5.4), then ampulla (2.4), and lowest in the canal system (1.0). These results reflect macrostructural variations in membrane shape, size, and thickness among the several chambers of the labyrinth. These decreasing stress proclivities parallel the decreasing frequency of histologic lesions found in documented cases of Meniere disease. Conclusions This model analysis of a human membranous labyrinth indicates that substantial disparities in stress exist among the several vestibular chambers due to macrostructural membrane configuration. Low stress levels in the canals are the result of thick highly curved membranes, and the high levels computed for the saccule reflect its thin and relatively flat membranes. These findings suggest that chamber configuration may be a factor controlling the progression of endolymphatic hydrops in Meniere disease.

Recurrent peripheral vestibulopathy: Is MRI useful for the diagnosis of endolymphatic hydrops in clinical practice?

OBJECTIVES

Recurrent peripheral vestibulopathy (RPV) is a public health problem, yet the aetiology remains unclear. Recent developments in MRI of endolymphatic hydrops (EH) allow for a better understanding of inner ear disorders. We intended to study the prevalence of EH in patients with RPV, in comparison to those with Meniere's disease (MD).

METHODS

MRI examinations were performed 4 hours after intravenous injection of gadoteric acid in 132 patients with RPV (n = 64) and MD (n = 68). Two radiologists retrospectively studied the prevalence and localization of EH in RPV and MD groups. Patients were graded based on the number and localization of hydrops, between 1 (EH in either cochlea or vestibule on one side) and 4 (EH in cochlea and vestibule on both ears).

RESULTS

We identified EH in 31 out of 64 patients and in 61 out of 68 patients in the RPV and MD groups, respectively. There was a significant difference regarding the number of subjects with EH between the two groups (p ≤ 0.01), with a higher average number of hydrops localization in MD group (p ≤ 0.01).

CONCLUSION

MRI may reveal EH in some cases among patients with RPV, suggesting a similar pathophysiological mechanism in comparison with MD.

KEY POINTS

• MRI may reveal endolymphatic hydrops in some patients with recurrent peripheral vestibulopathy. • We suggest a similar pathophysiological mechanism in recurrent vestibulopathy and Meniere's Disease. • MRI with delayed acquisition helps clinicians to assess patients with recurrent vestibulopathy. • The outcome would be to aid the development of adapted therapeutic strategies. • MRI of endolymphatic hydrops should probably be included in future diagnostic protocols.

Endolymphatic hydrops and Ménière's disease: a lesion meta-analysis

OBJECTIVE

To determine whether the distribution of membrane lesions associated with Ménière's disease is random, as might be expected from a pervasive process such as hydrops, or orderly, as might be expected if membrane resistance is graded.

METHOD

A meta-analysis of temporal bone reports on 184 specimens demonstrating endolymphatic hydrops was undertaken to determine membrane lesion evolution and distribution.

RESULTS

Lesion distribution was found to be orderly and cochleocentric. No random scattershot lesions were reported in any study. Disease always started in the cochlear apex, even in non-symptomatic cases, and then involved the saccule, utricle, ampullae and canal system in that precise sequence as the disease progressed.

CONCLUSION

The orderly lesion progression in the otopathology associated with Ménière's disease suggests that the hydropic process has a graded non-random effect on the labyrinth. These findings suggest a pathological staging system that may be useful in temporal bone evaluation.

Detection and grading of endolymphatic hydrops in Menière disease using MR imaging

BACKGROUND AND PURPOSE

Endolymphatic hydrops has been recognized as the underlying pathophysiology of Menière disease. We used 3T MR imaging to detect and grade endolymphatic hydrops in patients with Menière disease and to correlate MR imaging findings with the clinical severity.

MATERIALS AND METHODS

MR images of the inner ear acquired by a 3D inversion recovery sequence 4 hours after intravenous contrast administration were retrospectively analyzed by 2 neuroradiologists blinded to the clinical presentation. Endolymphatic hydrops was classified as none, grade I, or grade II. Interobserver agreement was analyzed, and the presence of endolymphatic hydrops was correlated with the clinical diagnosis and the clinical Menière disease score.

RESULTS

Of 53 patients, we identified endolymphatic hydrops in 90% on the clinically affected and in 22% on the clinically silent side. Interobserver agreement on detection and grading of endolymphatic hydrops was 0.97 for cochlear and 0.94 for vestibular hydrops. The average MR imaging grade of endolymphatic hydrops was 1.27 ± 0.66 for 55 clinically affected and 0.65 ± 0.58 for 10 clinically normal ears. The correlation between the presence of endolymphatic hydrops and Menière disease was 0.67. Endolymphatic hydrops was detected in 73% of ears with the clinical diagnosis of possible, 100% of probable, and 95% of definite Menière disease.

CONCLUSIONS

MR imaging supports endolymphatic hydrops as a pathophysiologic hallmark of Menière disease. High interobserver agreement on the detection and grading of endolymphatic hydrops and the correlation of MR imaging findings with the clinical score recommend MR imaging as a reliable in vivo technique in patients with Menière disease. The significance of MR imaging detection of endolymphatic hydrops in an additional 22% of asymptomatic ears requires further study.

Endolymphatic hydrops revealed by magnetic resonance imaging in patients with acute low-tone sensorineural hearing loss

OBJECTIVE

Acute low-tone sensorineural hearing loss (ALHL) has been reported to be associated with endolymphatic hydrops (EHs). However, evaluation of the size of the endolymphatic space has not been reported. We attempted to visualize EH in ALHL using magnetic resonance imaging (MRI).

STUDY DESIGN

Prospective diagnostic study.

SETTING

University hospital.

METHODS

We evaluated 25 ears of 25 unilateral ALHL patients. Three-tesla MRI was obtained 24 hours after intratympanic injection of gadolinium (Gd) (n = 5) or 4 hours after intravenous injection of Gd (n = 20). A radiologist blinded to the patients' clinical data classified the degree of EH in the vestibule and cochlea into 3 groups: none, mild, and significant.

RESULTS

On the affected sides, cochlear EH was recognized in 23 ears (92%) and was classified as significant EH (n = 15) or mild EH (n = 8); vestibular EH was detected in 22 ears (88%), classified as significant EH (n = 16) or mild EH (n = 6). Cochlear EH was more frequently observed in the affected ear than in the contralateral ear (90% versus 40%, p < 0.05).

CONCLUSION

In ALHL, EH was observed not only in the cochlea but also in the vestibule as in Ménière's disease.

Imaging of Ménière's disease after intravenous administration of single-dose gadodiamide: utility of subtraction images with different inversion time

For the separate visualization of endolymph, perilymph, and bone on a single image after intravenous injection of single-dose gadodiamide, we fused gray-scale inverted positive endolymph (PEI) with native positive perilymph (PPI) images, that is, we subtracted PEI from PPI. Subtraction significantly improved the contrast noise ratio between endolymph and perilymph and the subjective visibility score for endolymphatic space. The 24 patients with the suspect of Ménière's disease were included.

Diameter of the Cochlear Nerve in Endolymphatic Hydrops: Implications for the Etiology of Hearing Loss in Ménière's Disease

OBJECTIVE/HYPOTHESIS

Endolymphatic hydrops (ELH) is an important histopathological hallmark of Ménière's disease. Experimental data from human temporal bones as well as animal models of the disorder have generally failed to determine the mechanism by which ELH or related pathology causes hearing loss. Hair cell and spiral ganglion cell counts in both human and animal case studies have not, for the most part, shown severe enough deterioration to explain associated severe sensorineural hearing loss. However a limited number of detailed ultrastructural studies have demonstrated significant reductions in dendritic innervation densities, raising the possibility that neurotoxicity plays an important role in the pathology of Ménière's disease (MD) as well as experimental endolymphatic hydrops (ELH). This study tests the hypothesis that neurotoxicity is an important primary mediator of injury to the hydropic ear and is reflected in measurable deterioration of the cochlear nerve in the animal model of ELH. This study also explores the previously presented hypothesis that cochlear injury in ELH is mediated through the actions of nitric oxide (NO) by evaluating whether hearing loss or various measures of cochlear damage can be ameliorated by administration of an agent that limits excess production of NO.

STUDY DESIGN

Part one of the project involves the surgical induction of endolymphatic hydrops and correlation of long term hearing loss with histological parameters of ELH severity as well as cochlear nerve and eighth cranial nerve diameter measurements. In part two, aminoguanidine is administered orally to a separate set of hydropic animals in an attempt to limit cochlear injury presumably mediated by NO.

METHODS

Guinea pigs are subjected to surgical induction of unilateral endolymphatic hydrops after establishing baseline ABR thresholds at 2, 4, 8, 16, and 32 kHz. Threshold shifts are established prior to sacrifice at 4 to 6 months and temporal bones processed for light microscopy. Measurements of cochlear nerve and eighth cranial nerve maximal diameters as well as average maximal diameters are carried out and correlated to hearing loss and a semi-quantitative measure of hydrops severity. The identical experiments are carried out in animals treated with aminoguanidine, an inhibitor of inducible nitric oxide synthase.

RESULTS

: The mean maximal diameter (n = 14) of the hydropic cochlear nerve was significantly reduced (432.14 +/- 43.18 vs. 479.28 +/- 49.22 microns, P = .0025) as compared to the control nerve. This was also seen in measures of the eighth cranial nerve (855.71 +/- 108.82 vs. 929 +/- 81.53 microns, P = 0.0003). Correlation studies failed to show correlation between hydrops severity and a cochlear nerve deterioration index (r = -0.0614, P = .8348). Similarly, hearing loss severity failed to correlate with cochlear nerve deterioration (r = 0.1300, P = .6577). There was a significant correlation between hearing loss and hydrops severity (r = 0.6148, P = .0193). Aminoguanidine treated animals (n = 5) also sustained nerve deterioration to the same degree as non-treated animals and there appeared to be no protective effect (at the dosage administered) against ELH related hearing loss, hydrops formation, or nerve deterioration.

CONCLUSION

ELH results in significant deterioration of cochlear nerve and eighth cranial nerve maximal diameters in the guinea pig model. These findings are in accord with previous studies which detected ultrastructural evidence of dendritic damage and indicate that neural injury is of sufficient severity to result in light microscopic evidence of cochlear nerve and eighth cranial nerve deterioration. These data support the concept that the principle pathological insult in ELH is a form of neurotoxicity, especially in light of previous studies which indicate relative preservation of hair cells at similar points in time. The lack of correlation between the severity of hydrops and nerve deterioration suggests that nerve deterioration is independent of hydrops severity.

Pathophysiology of Meniere's syndrome: are symptoms caused by endolymphatic hydrops?

BACKGROUND

The association of Meniere's syndrome with endolymphatic hydrops has led to the formation of a central hypothesis: many possible etiologic factors lead to hydrops, and hydrops in turn generates the symptoms. However, this hypothesis of hydrops as being the final common pathway has not been proven conclusively.

SPECIFIC AIM

To examine human temporal bones with respect to the role of hydrops in causing symptoms in Meniere's syndrome. If the central hypothesis were true, every case of Meniere's syndrome should have hydrops and every case of hydrops should show the typical symptoms.

METHODS

Review of archival temporal bone cases with a clinical diagnosis of Meniere's syndrome (28 cases) or a histopathologic diagnosis of hydrops (79 cases).

RESULTS

All 28 cases with classical symptoms of Meniere's syndrome showed hydrops in at least one ear. However, the reverse was not true. There were 9 cases with idiopathic hydrops and 10 cases with secondary hydrops, but the patients did not exhibit the classic symptoms of Meniere's syndrome. A review of the literature revealed cases with asymptomatic hydrops (similar to the current study), as well as cases where symptoms of Meniere's syndrome existed during life but no hydrops was observed on histology. We also review recent experimental data where obstruction of the endolymphatic duct in guinea pigs resulted in cytochemical abnormalities within fibrocytes of the spiral ligament before development of hydrops. This result is consistent with the hypothesis that hydrops resulted from disordered fluid homeostasis caused by disruption of regulatory elements within the spiral ligament.

CONCLUSION

Endolymphatic hydrops should be considered as a histologic marker for Meniere's syndrome rather than being directly responsible for its symptoms.

Cellular changes of Reissner's membrane in Meniere's disease: human temporal bone study

OBJECTIVE

To study the cellular characteristics of Reissner's membrane (RM) in temporal bones (TBs) from patients with endolymphatic hydrops with symptoms of Meniere's disease (EH/+MD) and TBs with endolymphatic hydrops without symptoms of Meniere's disease (EH/-MD) in an effort to understand the role of endolymphatic hydrops in MD symptoms.

STUDY DESIGN

Comparative study of human TB histopathology.

METHODS AND MATERIALS

Epithelial and mesothelial cellularity of RM from control TBs, TBs from patients with EH/+MD, and TBs from patients with EH/-MD were compared. The cellularity of epithelial and mesothelial cell nuclei (defined as number of cells/100 microm width of RM) were counted along the width of RM. The width of RM was measured from the vestibular crest of the spiral ligament to the limbus spiralis.

RESULTS

The cellular densities of epithelial cells in the basal and middle turns of RM were significantly higher in the EH/+MD and EH/-MD groups compared with "controls." There was no difference in epithelial cellularity between EH/+MD and EH/-MD. There was a decrease in the number of mesothelial cells of RM in the basal turn in EH/+MD and EH/-MD groups (statistically significant only in EH/+MD group) when compared with controls. The number of mesothelial cells of RM in the middle turn in EH/+MD and EH/-MD groups were significantly decreased compared with normals.

DISCUSSION

Similar findings in cellularity of RM in temporal bones with EH/+MD and EH/-MD suggest that pathophysiologic mechanisms other than hydrops may be responsible for symptoms in Meniere's disease.

Vestibular Evoked Myogenic Potentials and Glycerol Testing

OBJECTIVES/HYPOTHESIS

The objective was to evaluate dizziness as the first symptom of endolymphatic hydrops, which could provide valuable information on the initial stages of endolymphatic hydrops development.

STUDY DESIGN

The present investigation was specifically designed to establish whether a combination of the traditional glycerol test and the vestibular evoked myogenic potential (VEMP) glycerol test is capable of diagnosing endolymphatic hydrops early and to identify potential Meniere's disease. The study was limited to patients who complained of dizziness as their only vestibular symptom.

METHODS

Thirty-eight consecutive patients with dizziness who had received no treatment were investigated. Each patient underwent glycerol testing measured with both conventional pure-tone audiometry and vestibular evoked myogenic potential testing. For the vestibular evoked myogenic potential glycerol test, an increase of more than 20% in both latency and amplitude after glycerol intake was considered an improvement. RESULTS In one patient, the reappearance of the vestibular evoked myogenic potentials was observed. In another six patients, there was an increase in the vestibular evoked myogenic potential amplitudes, unilaterally in four cases and bilaterally in two. One patient showed a bilateral improvement in amplitude and an unilateral amelioration in latency.

CONCLUSION

The assumption of saccular dilation as a sign of early Meniere's disease was not supported by the literature, which considered saccular hydrops as the final progression of the dilation of the endolymphatic compartments into the cochlea. These data seem to indicate that in our patients a saccular dysfunction rather than an early saccular hydrops has been documented, confirming vestibular evoked myogenic potential testing as an intriguing diagnostic option for a lesion of this structure. The vestibular evoked myogenic potential glycerol test proved capable of identifying dysfunctions of the saccule that were not otherwise detectable by the routine methods. Therefore, the vestibular evoked myogenic potential glycerol test should be considered as an additional method of diagnosis in patients with vertigo or dizziness.

Transtympanic electrocochleography: a 10-year experience

OBJECTIVE

To report the authors' experience with transtympanic electrocochleography during the past 10 years.

STUDY DESIGN

Retrospective case review.

SETTING

Otology/neurotology referral center.

PATIENTS

Transtympanic electrocochleography was performed on 2,421 ears of 2,140 patients from May 1990 to April 2000.

INTERVENTION

Clicks and tonebursts were used in electrocochleography testing. Summating potential/action potential ratio was calculated. Action potential latency shift by rarefaction and condensation clicks was measured. Cochlear microphonic was recorded.

MAIN OUTCOME MEASURE

An enlarged summating potential/action potential ratio (>0.40), broadened action potential waveform (>3 msec) or prolonged action potential latency shift (>0.2 msec) was considered to be indicative of endolymphatic hydrops. The presence of cochlear microphonic indicated hair cell survival.

RESULTS

In response to clicks, an enlarged summating potential/action potential ratio was found in 76.1% of ears and a broadened action potential waveform in 70%. Either an enlarged summating potential/action potential ratio or a broadened action potential waveform was observed in 78.4% of ears. In response to tonebursts, an enlarged summating potential/action potential ratio was found in 64.8%. The combined use of clicks and tonebursts yielded an enlarged summating potential/action potential ratio in 81.7%. Electrocochleography using tonebursts had the advantage of frequency selectivity. A prolonged action potential latency shift was found in 62.2% of ears with Ménière's disease. A significant association between an enlarged summating potential/action potential ratio and an action potential latency shift was noted (chi = 5.357, p = 0.021). An enlarged summating potential/action potential ratio was found 71% in Stage 1 of Ménière's disease, 82% in Stage 2, 85% in Stage 3, and 90% in Stage 4 (chi = 19.442, p = 0.000). An enlarged summating potential/action potential ratio was associated with the duration of the disease, 43% in the under 1-year group, and 100% in the more than 30-years group (chi = 33.555, p = 0.000). A large cochlear microphonic was present in 69% of ears with hearing levels greater than 40 dB.

CONCLUSION

Transtympanic electrocochleography using clicks and tonebursts is a reliable test to detect the presence of endolymphatic hydrops in Ménière's disease. A prolonged action potential latency shift evoked by rarefaction and condensation clicks is a useful addition to the application of electrocochleography in the diagnosis of Ménière's disease.

Etiology, pathophysiology of symptoms, and pathogenesis of Meniere's disease

Endolymphatic hydrops is the pathologic feature associated with Meniere's disease. The development of endolymphatic hydrops appears to arise from multifactorial inheritance with alteration of endolymphatic homeostasis. Various factors associated with the phenomenon of hydrops include functional or anatomic obstruction of endolymphatic flow, malabsorption of endolymph, genetic anomalies, vasodilation, allergy, viral infection, and autoimmunity.

Perilymphatic and Endolymphatic Pressure in the Guinea Pig After Distal Dissection of the Endolymphatic Sac

HYPOTHESIS

The study was designed to investigate whether endolymphatic pressure exceeds perilymphatic pressure in an endolymphatic hydrops model with a partially functioning endolymphatic sac.

BACKGROUND

Previous investigations of perilymphatic and endolymphatic pressure measurements during endolymphatic hydrops were done in a classic endolymphatic hydrops model, with a surgically blocked endolymphatic duct and sac. This model, in contrast to the clinical situation of Meniere's patients, totally lacks the functional contribution of the endolymphatic sac.

METHODS

In the guinea pig, a partially functioning endolymphatic sac was created via dissection of the distal portion of the sac from the sigmoid sinus. Three (n = 5) and 6 months (n = 3) later, perilymphatic and endolymphatic pressures were measured consecutively using a WPI 900A micropressure system.

RESULTS

It was observed that damage to the distal part of the endolymphatic sac caused endolymphatic hydrops in 58% of the cases. The hydrostatic pressure in hydropic ears did not differ from that of control ears. There was no pressure difference between the perilymphatic and endolymphatic compartments in ears with endolymphatic hydrops. The endocochlear potential in ears with hydrops was statistically significantly decreased (p < 0.002).

CONCLUSION

In a hydrops model developed to be more comparable to the histopathologic appearance of Meniere's disease in the inner ear, no hydrostatic pressure difference was measured between the perilymphatic and endolymphatic spaces. The only functional difference from control ears we found was a decreased endocochlear potential.

Meniere's disease and endolymphatic hydrops without Meniere's symptoms: temporal bone histopathology

We studied temporal bone histopathology in 21 ears with Meniere's disease and 24 ears with endolymphatic hydrops without Meniere's symptoms and compared the findings to those in 10 ears with presbycusis and 11 ears with normal hearing. Normal hearing ears showed less degeneration of cochlear structures than the other ears. In ears with endolymphatic hydrops without Meniere's symptoms, the degeneration of spiral ligament, hair cells, dendrites (peripheral processes) and apical spiral ganglion cells was more severe than in the other three groups. In ears with Meniere's disease and endolymphatic hydrops without Meniere's symptoms, the hair cells and dendrites were more affected than ganglion cells and there was no correlation between hair cell and ganglion cell degeneration. These findings suggest that a permanent threshold shift in late stage endolymphatic hydrops is not related to ganglion cell loss but rather to degeneration of sensory elements.

Ultrastructure of the endolymphatic sac in two-phase endolymphatic hydrops in the guinea pig

Two-phase endolymphatic hydrops is a subtle experimental model for Meniere's disease. Chronic dysfunction of the endolymphatic sac, induced by dissection of the most distal part without causing damage to the intermediate part, is combined with increased endolymph production induced by administration of aldosterone which stimulates the N/K-ATPase in the stria vascularis. A transmission electron microscopic study was performed on the endolymphatic sacs of four groups of guinea pig cochleas: controls: non-operated aldosterone-treated cochleas; operated (dissection of the endolymphatic sac) cochleas; operated and aldosterone-treated cochleas. Light and electron microscopy showed a normal morphology in the controls. Aldosterone treatment had no visible effect. Dissected ears revealed severe deviations. The epithelium of the intermediate sac was low, showed dilated lateral intercellular spaces indicating elevated fluid transport and displayed serious degenerative processes. Distally, the endolymphatic sac was completely blocked by newly formed bone. Additional aldosterone treatment had no cumulative effect on the dissected ears.

Low-frequency masking for detection of endolymphatic hydrops in patients with glaucoma

The coincidence of various eye and ear abnormalities has been described in the literature. Some authors discuss the possible existence of endolymphatic hydrops in patients with glaucoma. Whereas the current diagnostic tests for glaucoma are well-defined and evident, those for endolymphatic hydrops are not so reliable. This has made it difficult to accurately study the coincidence of endolymphatic hydrops and glaucoma. For better detection of endolymphatic hydrops, we performed low-frequency masking tests in 23 patients with primary open-angle glaucoma without signs of Ménìere's disease. The phase dependent sensitivity of the organ of Corti to a short test stimulus can be measured by applying a low-frequency masker tone to determine the modulation depth. Whereas the modulation depth in the normal hearing population is around 20-35 dB, the modulation depth in patients with Ménière's disease may be significantly decreased (5-10 dB), depending on the stage of disease. A decreased modulation depth was found in at least one ear in 19 of our 23 patients with glaucoma. Correlations between homeostatic mechanisms and their histological characteristics, e.g. melanocytes and their hormonal and enzymatic regulation, will be discussed. If the common pathogenesis of eye and ear lesions is better understood, it may be possible to develop new and more effective strategies for prevention and therapy.

Two-phase endolymphatic hydrops: a new dynamic guinea pig model

The classical guinea pig model for Meniere's disease, in which endolymphatic hydrops was achieved by destruction of the endolymphatic sac and obliteration of the endolymphatic duct, is a non-physiological profound model with shortcomings in relation to Meniere's disease as seen in patients. We developed a more subtle animal model; the two-phase endolymphatic hydrops. This model is based on a combination of chronic endolymphatic sac dysfunction, induced by slight destruction of the most distal part of the endolymphatic sac, and acute stress-induced endolymph production by stimulation of the Na/K-ATPase in the stria vascularis with aldosterone. Light microscopy of the fluid compartments of four groups of cochleas was used to examine them for the presence of endolymphatic hydrops: i) Normal (control) cochleas showed no hydrops; ii) some of the non-operated (no destruction) aldosterone-treated cochleas showed small degrees of hydrops mainly present in the basal turns; iii) mild dissection of the endolymphatic sac without administration of aldosterone produced a hydrops which was mainly present in the cochlear apex; iv) combination of chronic endolymphatic sac dysfunction and acute attacks of endolymph production by aldosterone administration revealed the most severe degrees of hydrops in all cochlear windings, damage to cochlear structures, and cellular disturbances of the epithelial lining of the endolymphatic sac. This new model may represent a more physiologic and dynamic approach to Meniere's disease and may explain the etiology of many symptoms in patients such as the fluctuant nature and the types of sensoneuronal hearing losses.

Ménière's disease

There now exists a vast literature on Ménière's disease. In this review, we examine closely the foundations of some of the current concepts regarding various aspects of the disorder, including definitions, clinical features, natural history, pathology, pathogenesis, pathophysiology, diagnosis and treatment. We will highlight areas where the current state of knowledge is incomplete and also suggest some avenues for further research.