Animal models of endolymphatic hydrops

Vestibular Aqueduct Size Correlates With the Degree of Cochlear Hydrops in Patients With and Without Menière's Disease

OBJECTIVE

To correlate the CT imaging findings of the visibility and size of the vestibular aqueduct (VA) with the degree of the cochlear hydrops determined in MRI late imaging of the hydrops. Study Design: Retrospective study. Setting: Tertiary referral center. Patients: A total of 127 patients (62 women, 65 men, average age 55.6 yrs): 86 of these were diagnosed with Menière's disease (American Academy of Otolaryngology-Head and Neck Surgery [AAO-HNS] criteria; 67 unilateral, 19 bilateral).

INTERVENTIONS

Temporal bone CT and hydrops MRI were performed in all patients.

MAIN OUTCOME MEASURES

Visibility/width of the VA in temporal bone CT and grade of cochlear hydrops evaluated by MRI.

RESULTS

The width of the VA is significantly smaller in patients diagnosed with Menière's disease (30% non-visible VA), compared with the patients who did not fulfill the diagnostic criteria of Menière's disease (12% non-visible VA) (double sided Spearman correlation, p < 0.001). In all ears of patients diagnosed with Menière's disease the width of the VA was significantly correlated with the degree of the cochlear hydrops (in cases of non-visible VA 65% [34/52] ears presented with hydrops grade 3 or 4; 13% [7/52] ears presented with hydrops grade 1 or 2 and 21% [11/52] ears showed no hydrops) (Spearman correlation p = 0.001/p < 0.01). This is also true for all ears that can be summarized as hydrophic ear disease (symptomatic ears that present with a hydrops in MRI).

CONCLUSIONS

The results of our study could confirm the importance of the VA in the pathogenesis of the endolymphatic hydrops in vivo.

Correlation between magnetic resonance imaging classification of endolymphatic hydrops and clinical manifestations and audiovestibular test results in patients with definite Ménière's disease

OBJECTIVES

The purpose was to evaluate magnetic resonance imaging (MRI) classification of endolymphatic hydrops with clinical features, audiological and vestibular tests in patients with definite unilateral Ménière's disease (MD).

METHODS

Thirty-eight patients were enrolled in this study. The severity of the main clinical symptoms, audiovestibular tests, and MRI, performed 4 hours after intravenous injection of gadobutrol to visualize inner ear compartments, were evaluated. Endolymphatic space dilatation was assessed using Barath and Bernaerts grading systems, and the correlation between the grade of the hydrops and clinical features was evaluated.

RESULTS

Using the Barath system, cochlear hydrops was visualized in 81.6% of affected ears, while vestibular was 63.2%. Sensitivity increased to 94.7% using Bernaerts' modification. Vestibular hydrops involving the utricle was present only among patients with cochlear and saccular endolymphatic space dilatation. There was a significant relationship between the hearing level and the vestibular hydrops degree in the Bernaerts scale. The grade of the hydrops correlated neither with the duration of MD nor with the severity of main clinical symptoms. Our study proved MRI to be a sensitive diagnostic tool in MD. The endolymphatic hydrops' grade correlates with the hearing level, which confirms endolymphatic space dilatation's role in hearing loss.

CONCLUSIONS

In our study, two similar MRI grading systems were used; however, several differences were found compared to one another. The Bernaerts scale was more sensitive than the Barath scale, and several relationships between the radiological and clinical data were found. Therefore, several MRI evaluating scales and correlating them with the clinical features are needed. The increased perilymphatic enhancement of the cochlea and an extra low-grade vestibular hydrops distinguished in the Bernaerts scale may increase MD diagnosis sensitivity. Magnetic resonance findings in MD support the clinical diagnosis and may help to understand MD pathophysiology better. This study adds to the knowledge and diagnostics in MD for healthcare to improve patients' treatment.

Pathophysiological mechanisms at the sources of the endolymphatic hydrops, and possible consequences

The mechanisms of ion exchanges and water fluxes underlying the endolymphatic hydrops phenomenon, remain indeterminate so far. This review intends to reposition the physical environment of the endolymphatic compartment within the inner ear, as well as to recall the molecular effectors present in the membranous labyrinth and that could be at the source of the hydrops.

MRI evaluation of the endolymphatic space in otosclerosis and correlation with clinical findings

PURPOSE

The purpose of this study was to investigate the clinical features of ears with otosclerosis and their correlation with endolymphatic hydrops and blood-labyrinth barrier (BLB) impairment on 3T magnetic resonance imaging (MRI).

MATERIALS AND METHODS

This was a single-center retrospective imaging study. Thirty-nine ears from 29 patients (17 men, 12 women; mean age 52±12 [SD] years; range 27-74 years) with non-operated otosclerosis were included. All patients underwent three-dimensional fluid attenuated inversion recovery (FLAIR) MRI sequences performed 4hours after the intravenous administration of a single dose of gadolinium-based contrast material. MRI examinations were analyzed by two radiologists for the presence of saccular hydrops (SH) and BLB impairment. Results of MRI examinations were compared with clinical findings, hearing levels and extent of otosclerotic lesions based on high-resolution computed tomography findings. BLB impairment was evaluated using the signal intensity ratio, ratio of intensities between the basal turn of the cochlea and the medulla.

RESULTS

SH was observed in 1/39 (3%) otosclerotic ears and BLB impairment in 8/39 (21%) while 8/29 patients with otosclerosis (28%) had vertigo. No significant associations were found between SH or BLB impairment on MRI, and the presence of vertigo or the degree of sensorineural hearing loss.

CONCLUSION

Clinical manifestations of otosclerosis (sensorineural hearing loss and rotatory vertigo) were not significantly associated with MRI findings such as BLB impairment and endolymphatic hydrops. SH was only observed in one patient with obstruction of the vestibular aqueduct by an otosclerotic focus.

The Correlation Between Endolymphatic Hydrops and Clinical Features of Meniere Disease

OBJECTIVES

The purpose of this study was to investigate the grades of endolymphatic hydrops determined by gadolinium-contrast magnetic resonance (MR) and correlation to the clinical features in patients with Meniere disease.

STUDY DESIGN

Prospective study.

METHODS

A total of 24 patients suffering from unilateral Meniere disease with either definite or probable clinical diagnosis were included. The duration of vertigo, duration of tinnitus, duration of vertigo attacks, hearing thresholds, and canal paresis (CP) value of caloric tests were assessed. Three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging (MRI) was performed 4 hours after intravenous injection of double dose of gadobutrol (Gd) to show endolymph and perilymph, and the grades of endolymphatic hydrops were measured. Additionally, the correlation between clinical features and the grades of endolymphatic hydrops of cochlea and vestibular were evaluated.

RESULTS

Different grades of the endolymphatic hydrops in the impaired ear were revealed by MRI. The Spearman correlation showed a strong correlation between the hearing thresholds of low, middle, and high tone and the grades of cochlea and vestibular hydrops (P < .05); However, no significant correlation between the duration of vertigo, duration of tinnitus, duration of vertigo attacks, CP value, and endolymphatic hydrops was determined (P > .05).

CONCLUSION

By visualizing the endolymph and perilymph of inner ear in patients with Meniere disease assisted with intravenous injection of double doses of Gd, the grades of endolymphatic hydrops could be assessed. As a result, the grades of endolymphatic hydrops in patients with Meniere disease can be used to predict the level of hearing impairment.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E144-E150, 2021.

The effect of noise exposure on the vestibular systems of dental technicians

BACKGROUND

Noise exposure is the primary cause of acquired hearing loss in several occupational settings, including dental laboratories and clinics. However, the impact of noise exposure on the vestibular system is not as well researched.

PURPOSE

To investigate the nature of vestibular damage caused by working in dental laboratories and clinics with high levels of noise exposure due to loud dental equipment.

RESEARCH DESIGN

A descriptive, case study design was used to evaluate the vestibular function of dental technicians.

STUDY SAMPLE

Out of 30 dental technicians, 5 males who had been working for several years in dental settings were selected based on their reports of severe symptoms of imbalance.

DATA COLLECTION

Audiologic evaluations were conducted in the vestibular unit of the Doctor Tarek Khrais Center in Amman, Jordan, for one year. Each subject underwent several hearing tests, which included otoscopic examination, pure tone audiometry (PTA), impedance measurements, and speech testing. Assessment of vestibular function was then conducted using a diagnostic test battery which included electrocochleography, ocular vestibular evoked myogenic potentials (oVEMP), cervical vestibular evoked myogenic potentials (cVEMP), positional testing using the Thomas Richard-Vitton (TRV) chair, and standing stability testing.

RESULTS

All test subjects experienced some form of vestibular impairment, including benign paroxysmal positional vertigo (BPPV), endolymphatic hydrops (Meniere disease), or a combination of both. Three out of five cases displayed little or no hearing loss, indicating that vestibular function is more at risk than hearing acuity to continuous noise exposure in dental settings.

CONCLUSIONS

Exposure to loud noise in dental laboratories severely impacts the functioning of the vestibular system of the inner ear more than the cochlea. The main clinical implication of this study is that regular vestibular assessments are a necessity for dental technicians.

Association of Meniere's disease and retinal vascular calibre: a prospective observational study in China

OBJECTIVE

It is believed that Meniere's disease (MD) is associated with vascular disorders, but few studies have reported the relationship between retinal vascular disorders and MD. We evaluated and compared the retinal vascular calibres in patients with MD with healthy subjects matched for age, sex and vascular risk factors using retinal photographs to explore the association between MD and retinal vascular calibre.

STUDY DESIGN

A prospective study.

SETTING

Tertiary referral centre.

PARTICIPANTS

Sixty patients with MD and 62 healthy subjects matched for age, sex and vascular risk factors were enrolled in this study. Twenty-four patients with MD had migraines, and 36 patients with MD did not have migraines.

MAIN OUTCOME MEASURE

Retinal vascular calibres were calculated and compared not only between patients with MD and healthy subjects but also between subgroups of patients with MD.

RESULTS

Compared with healthy subjects, patients with MD had a slightly larger retinal artery calibre (126.30±10.45vs 119.61±15.86, p=0.006) and a higher retinal artery/vein ratio (0.79±0.09vs 0.75±0.10, p=0.005). Among patients with MD, those with migraines had a larger retinal artery calibre (130.73±11.55vs 123.35±8.61, p=0.006) than those without migraines. Moreover, the presence of migraines and the high frequency of vertigo attacks appeared to increase the retinal artery calibre.

CONCLUSIONS

Our study suggests that a relationship exists between retinal vascular calibre and MD. Although the pathophysiological relationship between migraine and MD remains unclear, the presence of migraine attacks may aggravate endolymphatic hydrops (EH) and accelerate the outflow of EH in patients with MD. More extensive studies are required to explore the association between retinal vascular calibre and MD.

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.

Otopathologic Changes in the Cochlea following Head Injury without Temporal Bone Fracture

Objective

Hearing loss following temporal bone (TB) fracture may result from direct transection of the middle and inner ear. The pathophysiology of hearing loss due to head injury without TB fracture, however, is not well understood. Few reports describe otopathologic findings. Herein, we investigate the pathologic findings of patients who sustained a head injury without evidence of a TB fracture.

Study Design

Otopathology study.

Setting

Otopathology laboratory.

Subjects

Subjects with a history of head injury without TB fracture.

Methods

The TBs of patients with head injury were evaluated by light microscopy. Inner ear anatomy was evaluated, including counts of spiral ganglion cells (SGCs), hair cells, pillar cells, atrophy of the stria vascularis, and the presence of endolymphatic hydrops. SGC counts were compared with those of historical age-matched controls.

Results

All cases (N = 6 TBs) had evidence of inner ear pathology. Of the 6 cases, 2 (33%) had severe loss of hair cells in all 3 turns of the cochlea, and 4 (67%) cases demonstrated moderate to severe loss at the basal turn of the cochlea. Four cases had scattered atrophy of the stria vascularis, and 3 (50%) had cochlear hydrops. The number of total SGCs was decreased, with an average 53% loss (range, 25%-79%) as compared with controls. The SGC count loss was evenly distributed along Rosenthal’s canal.

Conclusions

Patients with a history of head injury without TB fracture demonstrate inner ear pathology. Further studies are necessary to determine if otopathology findings are directly attributable to trauma.

In vivo imaging of saccular hydrops in humans reflects sensorineural hearing loss rather than Meniere's disease symptoms

OBJECTIVES

A case-controlled imaging study demonstrated that saccular hydrops was specific to Meniere's disease (MD), but only present in a subset of patients. Here, we compared patients with definite MD, vertigo and sensorineural hearing loss (SNHL) to elucidate the relationship between saccular hydrops and extent of SNHL.

METHODS

In this prospective study, we performed 3D-FLAIR sequences between 4.5 and 5.5 h after contrast media injection in patients with MD (n=20), SNHL (n=20), vertigo (n=20) and 30 healthy subjects. Two radiologists independently graded saccular hydrops. ROC analysis was performed to determine the hearing loss threshold to differentiate patients with saccular hydrops.

RESULTS

Saccular hydrops was found in 11 of 20 MD patients, 10 of 20 SNHL patients and in none of the vertigo patients and healthy subjects. In SNHL patients, 45 dB was the threshold above which there was a significant association with saccular hydrops, with sensitivity of 100 % and specificity of 90 %. In MD patients, 40 dB was the threshold above which there was a significant association with saccular hydrops, with sensitivity of 100 % and specificity of 44 %.

CONCLUSIONS

Our results indicate saccular hydrops as a feature of worse than moderate SNHL rather than MD itself.

KEY POINTS

• MRI helps clinicians to assess patients with isolated low-tone sensorineural hearing loss. • Saccular hydrops correlates with sensorineural hearing loss at levels above 40 dB. • Vertigo patients without sensorineural hearing loss do not have saccular hydrops. • Saccular hydrops is described in patients without clinical diagnosis of Meniere's disease.

Evaluation of the usefulness of three-dimensional optical coherence tomography in a guinea pig model of endolymphatic hydrops induced by surgical obliteration of the endolymphatic duct

Optical coherence tomography (OCT) has advanced significantly over the past two decades and is currently used extensively to monitor the internal structures of organs, particularly in ophthalmology and dermatology. We used ethylenediamine tetra-acetic acid (EDTA) to decalcify the bony walls of the cochlea and investigated the inner structures by deep penetration of light into the cochlear tissue using OCT on a guinea pig model of endolymphatic hydrops (EH), induced by surgical obliteration of the endolymphatic duct. The structural and functional changes associated with EH were identified using OCT and auditory brainstem response tests, respectively. We also evaluated structural alterations in the cochlea using three-dimensional reconstruction of the OCT images, which clearly showed physical changes in the cochlear structures. Furthermore, we found significant anatomical variations in the EH model and conducted graphical analysis by strial atrophy for comparison. The physical changes included damage to and flattening of the organ of Corti—evidence of Reissner's membrane distention—and thinning of the lateral wall. These results indicate that observation of EDTA-decalcified cochlea using OCT is significant in examination of gradual changes in the cochlear structures that are otherwise not depicted by hematoxylin and eosin staining.

Prox1 expression in the endolymphatic sac revealed by whole-mount fluorescent imaging of Prox1-GFP transgenic mice

This study describes a technical breakthrough in endolymphatic sac research, made possible by the use of the recently generated Prox1-GFP transgenic mouse model. Whole-mount imaging techniques through the decalcified temporal bone and three-dimensional observations of Prox1-GFP mouse tissue revealed the positive labeling of the endolymphatic sac in adult stage, and allowed, for the first time, the GFP-based identification of endolymphatic sac epithelial cells. Prox1 expression was observed in all parts of the endolymphatic sac epithelia. In intermediate portion of the endolymphatic sac, mitochondria-rich cells did not express Prox1, although ribosome-rich cells showed strong GFP labeling. The anatomical relationship between the endolymphatic sac and the surrounding vasculature was directly observed. In the endolymphatic sac, expression of Prox1 may suggest progenitor cell-like pluripotency or developmental similarity to systemic lymphatic vessels in other organs. This whole-mount imaging technique of the endolymphatic sac can be combined with other conventional histological, sectioning, and labeling techniques and will be very useful for future endolymphatic sac research.

Long-term administration of vasopressin can cause Ménière's disease in mice

CONCLUSION

A new murine model of Ménière's disease has been developed, based on long-term administration of vasopressin. Induction of vestibular dysfunction in the present animal model can cause additional stress, by reducing inner ear blood flow. Latanoprost, a selective agonist for the FP prostanoid receptor, may become a new remedy for Ménière's disease.

OBJECTIVE

The purpose of this study was to develop a more suitable animal model, with a closer resemblance to the pathophysiological process in Ménière's disease.

METHODS

Adult CBA/J or ICR mice were treated by subcutaneous injection of vasopressin for 5 days up to 8 weeks. Morphological analyses were performed of the cochlea, vestibular end organs and endolymphatic sac. The effect of latanoprost on the development of endolymphatic hydrops was also examined.

RESULTS

All experimental animals showed mild to moderate endolymphatic hydrops, increasing in severity as the vasopressin treatment was prolonged. Animals treated with vasopressin for 8 weeks showed severe endolymphatic hydrops with partial loss of outer hair cells and spiral ganglion cells. These animals also had a reversible vestibular dysfunction following intratympanic injection of epinephrine. Latanoprost inhibited the development of endolymphatic hydrops caused by vasopressin.

Geometrical and volume changes of the membranous vestibular labyrinth in guinea pigs with endolymphatic hydrops

OBJECTIVE

To evaluate geometrical and volume changes of membranous vestibular labyrinths in guinea pigs after endolymphatic hydrops (EH).

METHODS

The membranous labyrinths of normal guinea pigs and of those with EH for 4 and 8 weeks were reconstructed after being scanned using micro-computed tomography subseqent to being stained in osmium tetroxide (OsO4). The diameters and volumes of the semicircular ducts, ampullae, utricles and saccules were measured based on the three-dimensional models.

RESULTS

The diameters of the ampullae and utricles of EH guinea pigs were greater than those of the normal guinea pigs, while there were no significant differences in the diameters of the semicircular ducts among all groups. The volumes of ampullae, utricles and saccules of the EH groups were greater than those of the control group, but there were no changes in volumes of semicircular ducts after EH.

CONCLUSION

The dilations of the membranous vestibular labyrinth in guinea pigs with EH mainly occur at the ampullae, utricles and saccules.

Expression of osmotic stress protein 94 in murine endolymphatic hydrops model

CONCLUSION

The up-regulation of osmotic stress protein 94 (OSP94) in the murine endolymphatic hydrops (EH) models suggests that OSP94 might be involved in cellular adaptation in response to ionic and osmotic stress in the murine inner ear.

OBJECTIVES

The purpose of the present study was to investigate the expression of OSP94 in cochlear tissues of the murine EH models and control animals.

METHODS

Nine adult BALB/c mice were treated with both intratympanic injection of lipopolysaccharide and intraperitoneal administration of aldosterone to induce EH. Nine mice were used as control animals. The expression level of OSP94 in the EH and control groups was compared using immunohistochemistry and real-time RT-PCR.

RESULTS

Immunohistochemical staining of tissues in the EH group showed an up-regulation of OSP94 expression in the cochlea, especially in the stria vascularis and Reissner's membrane. Quantitative real-time PCR analysis also showed that transcription of the OSP94 gene in the cochlea was significantly up-regulated in the EH group.

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.

Specific RNA collection from the rat endolymphatic sac by laser-capture microdissection (LCM): LCM of a very small organ surrounded by bony tissues

Laser-capture microdissection (LCM) is an excellent tool to selectively obtain target tissue or cells. The endolymphatic sac (ES) is part of the inner ear, and a large part of the ES is located in the temporal bone. The rat ES is conventionally harvested using stereomicroscopy. In this method, contamination is unavoidable because of its size and location; therefore, additional checks, such as in situ hybridization, are necessary to confirm the cellular localization, and quantitative analysis is difficult in the ES. We have shown a selective epithelial tissue method using LCM to obtain RNA without contamination from ES epithelial tissue.

Genetic investigations of Meniere's disease

Meniere's disease remains a disorder of unknown origin despite the collective efforts to determine the pathogenesis, although experts have long recognized that disease development likely has some heritable component. Although genetic studies of Meniere's disease have been inconclusive, increasing knowledge of human genetic structure and mutation and investigative techniques have potential to further understanding of this disorder.

Magnetic resonance imaging of guinea pig cochlea after vasopressin-induced or surgically induced endolymphatic hydrops

Objective: To investigate the ability to detect the in vivo cochlear changes associated with vasopressin-induced and surgically induced endolymphatic hydrops using MRI at 3 tesla (T).

Study Design: Prospective, animal model.

Setting: Animal laboratory.

Subjects and Methods: In group 1, five guinea pigs underwent post–gadolinium temporal bone MRI before and after seven and 14 days of chronic systemic administration of vasopressin by osmotic pump. In group 2, five guinea pigs underwent temporal bone MRI eight weeks after unilateral surgical ablation of the endolymphatic sac. Three-tesla high-resolution T1-weighted sequences were acquired pre- and postcontrast administration. Region of interest signal intensities of the perilymph and endolymph were analyzed manually. Quantitative evaluation of hydrops was measured histologically.

Results: Gadolinium preferentially concentrated in the perilymph, allowing for distinction of cochlear compartments on 3.0-T MRI. The T1-weighted contrast MRI of vasopressin-induced hydropic cochlea showed significant increases in signal intensity of the endolymph and perilymph. Surgically induced unilateral hydropic cochlea also showed increased signal intensity, compared with the control cochlea of the same animal, but less of an increase than the vasopressin group. The histological degree of hydrops induced in the vasopressin group was comparable to previous studies.

Conclusions: In vivo postcontrast MRI of the inner ear demonstrated cochlear changes associated with chronic systemic administration of vasopressin and surgical ablation of the endolymphatic sac. Understanding the MRI appearance of endolymphatic hydrops induced by various methods contributes to the future use of MRI as a possible tool in the diagnosis and treatment of Ménière's disease.

Effect of inner ear blood flow changes in Ménière's model mice

CONCLUSIONS

The endolymphatic sac (ES) is important for inner ear fluid homeostasis. A dysfunctional ES can cause vertigo attacks following additional stress such as a sudden change in endolymphatic volume and/or pressure, or restricted inner ear blood flow.

OBJECTIVE

The purpose of this study was to elucidate the mechanism of vertigo attacks in Ménière's disease.

MATERIALS AND METHODS

Adult CBA/J mice were given an intratympanic injection of lipopolysaccharide and an intraperitoneal injection of aldosterone. These 'model' animals had epinephrine or sodium nitroprusside (SNP) instilled into the middle ear cavity. Cochleae, vestibules, and endolymphatic sacs were studied morphologically by light microscopy.

RESULTS

The injection of epinephrine into the model animals reduced the endolymphatic hydrops in the cochlea, but also produced mild hydrops in the vestibule, which was never observed in untreated (control) animals. The ES did not react to epinephrine in the normal way. Injection of SNP did not cause any changes.

Effect of acute endolymphatic hydrops overload on the endolymphatic sac

CONCLUSIONS

Homeostasis of endolymph volume is a complex mechanism, in which the endolymphatic sac (ES) may play an important role.

OBJECTIVES

To elucidate the effect of acute endolymphatic hydrops (EH) on the ES and to gain further information about the volume and pressure regulative function of the ES.

MATERIALS AND METHODS

Distilled water was injected into the middle ear cavity of adult CBA/J mice. The ESs were studied morphologically by light and transmission electron microscopy.

RESULTS

Mild EH was found, particularly in the upper turn of the cochlea. Acute EH led to an increase in the size of the ES lumen, accompanied by collapse of the lateral intercellular spaces and dense perisaccular tissue, changes which had reversed 2 h after the injection.

A new animal model for Ménière's disease

CONCLUSION

A new murine model for the study of Ménière's disease has been developed by treatment with both lipopolysaccharide (LPS) and aldosterone. Induction of vestibular dysfunction in the hydropic animal model may entail additional stress such as reduced inner ear blood flow, and sudden acute changes in endolymph volume and/or pressure.

OBJECTIVE

The purpose of this study was to develop a more suitable animal model, showing closer resemblance to the pathophysiological process in Ménière's disease.

MATERIALS AND METHODS

Adult CBA/J mice were treated by intratympanic injection of LPS, intraperitoneal injection of aldosterone, or injection of both LPS and aldosterone. Morphological analyses were performed in the cochlea and endolymphatic sac.

RESULTS

All experimental animals showed mild to moderate endolymphatic hydrops. Those treated with both LPS and aldosterone showed reversible vestibular dysfunction after the intratympanic injection of epinephrine.

La surdité brusque idiopathique n'est pas, aujourd'hui, une urgence sensorielle

OBJECTIVES

To evaluate the influence of the treatment delay for sudden sensorineural hearing loss (SSHL) on the final hearing recovery and the prognostic value of the audiometric shapes and the hearing recovery at the end of treatment.

PATIENTS AND METHODS

Prospective study including 321 patients admitted in the emergency care center for a recent idiopathic SSHL. Classification according to the audiometric shape in 5 types. All patients received steroids (1 mg/kg per day) and, in case of ascending shape, steroids and mannitol during 6 days. Hearing recovery was evaluated according to the following parameters: 1) hearing recovery (initial PTA-PTA at D6 or D30); 2) incidence of hearing recovery (initial PTA-PTA at D6 or D30)/initial PTA x 100%).

RESULTS

Whatever the audiometric type, delay in initiating treatment did not have any influence on the final outcome. Audiometric classification had a good prognostic value, since the ascending shape had a better hearing recovery than descending shape or the sub or total anacusis. Hearing recovery at D6 is a prognostic factor on the final outcome.

CONCLUSIONS

Idiopathic SSHL cannot be considered, nowadays, as an otologic emergency.

Unbiased stereological estimation of the spiral ligament and stria vascularis volumes in aging and Ménière's disease using archival human temporal bones

The present study applies the unbiased stereological technique-Cavalieri principle to measure the volumes of the stria vascularis (SV) and the spiral ligament (SL) using postmortem archival human temporal bones from normal young and older subjects and subjects with Ménière's disease. Normative data was obtained from subjects without ages ranging from 15 to 84 years old who had no history of audiovestibular disease (N=25). For comparison purposes, the normative specimens were divided into three groups: group 1 (n=8) had ages ranging from 15 to 38 years old, average age=23.9; group 2 (n=8) had ages ranging from 51 to 59 years old, average age=55.1; group 3 (n=9) had ages ranging from 64 to 84 years old, average age=74.3. The average SV volume of group 3 (0.479 mm3) was significantly lower than that of group 1 (0.705 mm3) (p<0.0005) and was significantly lower than that of group 2 (0.603 mm3) (p=0.01). The average SL volume of group 3 (8.42 mm3) was significantly lower than that of group 1 (9.54 mm3) (p<0.05), but was not significantly lower than that of group 2 (8.58 mm3). Five subjects with Ménière's disease, confirmed by histopathological examination (ages ranging from 63 to 91 years old, average age=73.4), were studied. The average SV volume in Ménière's subjects (0.378 mm3) was significantly lower than age-matched controls (p<0.05). The average SL volume in Ménière's subjects (7.01 mm3) was also significantly lower than age-matched controls (p<0.05). The SV and SL volumes were unaffected by gender. The present study demonstrates for the first time the use of the unbiased stereological technique-Cavalieri principle-as a reliable and efficient method to obtain volumetric estimates of the SV and the SL by using archival human temporal bone specimens.

Aquaporins and Meniere's disease

PURPOSE OF REVIEW

Review of the role of aquaporins in inner ear homeostasis and potential role in the pathogenesis of Meniere's disease.

RECENT FINDINGS

Recent findings include the immunolocalization of aquaporins in the inner ear of mouse, rat, and human to cell types that are likely to undergo high ionic perturbances (e.g. potassium flux) and to putative areas of endolymph resorption or cycling.

SUMMARY

The expression of aquaporins and related proteins in the human cochlea and vestibular periphery resembles the distribution found in animal models, suggesting a critical role of aquaporins in inner ear water homeostasis and their potential role in the pathogenesis of Meniere's disease.

Idiopathic Sudden Sensorineural Hearing Loss Is Not an Otologic Emergency

OBJECTIVE

To investigate whether delay in treatment has any influence on the audiometric outcome at Day 30 in idiopathic sudden sensorineural hearing loss.

STUDY DESIGN

Prospective study.

SETTING

Otorhinolaryngologic emergency center in Paris, France.

PATIENTS

Three hundred forty-seven consecutive cases of sudden sensorineural hearing loss were examined. A neurologic or retrocochlear cause was revealed in 17 cases. Four additional cases were lost for follow-up. Three hundred twenty-six cases of "idiopathic" sensorineural hearing loss seen within 7 days of onset were enrolled and classified by type according to five audiogram shapes: low tone (Type A), flat (Type B), high tone (Type C), cup-shaped (Type D) or total or subtotal (Type E). Because of loss for follow-up, the hearing outcome at 1 month could be evaluated in only 249 cases.

INTERVENTION

All 326 patients were given 1 mg/kg per day corticosteroids intravenously for 6 days and 500 ml mannitol 10% in the subgroup presenting ascending audiometric shape.

MAIN OUTCOME MEASURES

The following parameters were used. The first parameter was hearing recovery (initial PTA-PTA at Day 6 or Day 30). It was considered as complete if final PTA was below 25 dB. The second parameter was incidence of hearing recovery based on the following formula: (initial PTA-PTA on a given test day)/(initial PTA) x 100%. Using regression analysis and ANOVA, the audiometric outcome was analyzed at Day 6 and Day 30 as a function of the day of onset of treatment and of the audiometric type.

RESULTS

Whatever the audiometric type, there was no significant difference in final outcome whether the treatment was started within the first 24 hours or within the first week.

CONCLUSIONS

Delay in initiating treatment does not appear to influence the final degree of hearing loss. Idiopathic sudden sensorineural hearing loss cannot be considered as an otologic emergency.

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.

Intralabyrinthine fluid dynamics: Meniere disease

PURPOSE OF REVIEW

Meniere disease has long been postulated to be a disorder of intralabyrinthine fluid dynamics.

RECENT FINDINGS

More recent developments in this field indicate that the control of fluid movement may be at a cellular level and that hormonal influence may be important.

SUMMARY

The control of fluid and ion movements through aquaporins and gap junctions in the cell membranes are creating new perspectives in the mechanism of development of endolymphatic hydrops as well as potential methods for treatment. Intralabyrinthine fluid dynamics also play a role in the ability to locally deliver drugs to the inner ear through the middle ear.

Evoked otoacoustic emissions in patients with Ménière's disease

HYPOTHESIS

This study investigated whether otoacoustic emissions (OAEs) in patients with Ménière's disease show abnormal properties.

BACKGROUND

Patients with Ménière's disease experience vertigo, tinnitus, and hearing loss. OAEs are sounds generated in the inner ear, and their presence is associated with normal hearing.

METHODS

Click-evoked OAEs and distortion product OAEs were measured in 100 patients with Ménière's disease.

RESULTS

The incidence of the emissions in affected ears (56%) was lower than in unaffected (i.e., contralateral) ears (85%). The mean emission amplitude in affected ears was also significantly lower (2.6 dB), and the mean amplitude in unaffected ears was lower than in normal-hearing ears (5.3 dB). These differences were likely caused by the hearing loss involved. Further, ears with OAEs clearly showed smaller hearing losses than ears without OAEs (24-dB difference). The average hearing loss showed correlations with the emission amplitudes, although this correlation was not very strong; when plotted against the smallest hearing loss, a certain upper boundary for the emission amplitude was present. Also, the amplitude of click-evoked OAEs showed a considerable correlation with the largest of the three distortion product OAEs.

CONCLUSION

OAEs in patients with Ménière's disease differed from those in normal-hearing ears but did not differ from those in non-Ménière's ears with equivalent hearing loss. This was best observed by comparing emission amplitude with smallest hearing loss instead of mean hearing loss.

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.

The three faces of vestibular ganglionitis

We present temporal bone and clinical evidence that common syndromes of recurrent vertigo are caused by a viral infection of the vestibular ganglion. In the present series, histopathologic and radiologic changes in the vestibular ganglion and meatal ganglion were consistent with a viral inflammation of ganglion cells in cases of Meniere's disease, benign paroxysmal positional vertigo, and vestibular neuronitis. Clinical observations of multiple neuropathies involving cranial nerves V, VII, and VIII on the same side in patients with recurrent vertigo are best explained by a cranial polyganglionitis caused by a neurotrophic virus, which is reactivated by a stressful event later in life. The reactivation of the latent virus may manifest as one of the above vertigo syndromes, depending on the part of the vestibular ganglion that is inflamed, the type and strain of the virus, and host resistance.

Menière's disease: pathophysiology and treatment

Menière's disease is defined by the association of 4 symptoms: vertigo attacks, fluctuating hearing loss, tinnitus and an auricular plenitude sensation. The pathophysiology is commonly explained by a distension of membranous labyrinth by the endolymph, equally called endolymphatic hydrops. Recent studies also tend to relate the disease to immune mechanisms. The treatment is medical in the majority of patients but there is no international consensus on the management of the different stages of Menière's disease. Regarding the lack of clinical studies clearly demonstrating the effectiveness of a certain therapy or another. the recommendations are usually based on the empirical experience of practitioners and on the observation of a marked amelioration at 2 years of treatment in the majority of patients. The treatment of the acute phase of Menière's disease is basically symptomatic. Vestibular suppressant drugs have a well-established record in controlling acute attacks of vertigo. Most have variable anticholinergic, anti-emetic and vestibular sedative effects. If necessary, the administration of benzodiazepines will help to alleviate anxiety. Long term management of Menière's disease includes a low salt diet, the use of diuretics in the post-crisis phase, and the very common use in Europe of histaminergic agents. Corticosteroids are used in bilateral forms of Menière's disease, particularly if an autoimmune basis is suspected. All authors insist on the interest and the importance of regular follow-up, especially with regard to the psychological status and responsiveness to treatment of the patient. Surgical indications are rare and the least invasive procedures are used first. The choice of the procedure should take into consideration the need to preserve the auditory function of the patient.

Diagnosis of endolymphatic hydrops in vivo with magnetic resonance imaging

HYPOTHESIS

High-resolution magnetic resonance imaging (MRI) at 1.5 T preferentially enhances the perilymph over endolymph after administration of contrast with gadodiamide, which allows for differentiation of the membranous labyrinth. Furthermore, this imaging allows for the detection of endolymphatic hydrops.

BACKGROUND

Endolymphatic hydrops is believed to be associated with a number of ear diseases, including Ménière's disease. Although the pathologic changes of overaccumulation of endolymph in the inner ear are obvious on postmortem histologic examination of the temporal bone, they have yet to be observed in a living organism. Previous attempts to visualize this condition with high-resolution contrast-enhanced computed tomographic imaging and MRI have been unsuccessful.

METHODS

Healthy pigmented guinea pigs underwent a unilateral surgical ablation of the endolymphatic sac to create endolymphatic hydrops in the ear. High-resolution temporal bone imaging was performed by use of a 1.5-T MRI system. Two-dimensional images were acquired by a spin-echo technique with and without contrast enhancement by gadodiamide.

RESULTS

T1-weighted gadodiamide contrast-enhanced MRI of the midmodiolar level of the cochlea demonstrated that the perilymph appeared to be preferentially enhanced relative to the endolymph, resulting in a clear distinction between the scalae of the inner ear. The contrast-enhanced T1-weighted MRI of the midmodiolar level of the hydropic cochlea demonstrated a significantly enlarged scala media in comparison with the normal cochlea in the same animal.

CONCLUSION

The demonstration of endolymphatic hydrops has been possible for the first time in vivo by the use of a standard 1.5-T MRI system. This research has important clinical implications: Specifically, this technique may allow for the noninvasive diagnosis of Ménière's disease.

Menière's disease as a manifestation of vestibular ganglionitis

OBJECTIVE

To present morphologic evidence of viral-induced vestibular nerve pathology in Menière's Disease (MD). MATERIAL STUDIED: Twelve temporal bones (TB) from 8 patients with the clinical symptoms of MD.

RESULTS

There was endolymphatic hydrops (EH) and perilymphatic fibrosis in 10 of the 12 TB from MD patients. Of the 10 TB with EH of the pars inferior, 3 also contained outpouchings in the pars superior (utricle and canals), and 3 showed apical spiral ganglion cell loss. Focal vestibular nerve axonal degeneration was observed in all but one TB.

CONCLUSION

Morphologic changes in TB of patients with MD, and clinical observations in patients with recurrent vestibulopathy, support the concept that the pathologic mechanism responsible for auditory and vestibular symptoms in MD may be reactivation of a latent viral vestibular ganglionitis.

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.

Effect of furosemide on basal lamina anionic sites in guinea pig labyrinth

The authors studied the effects of acute furosemide administration on the basal lamina (BL) anionic sites in the stria vascularis, ampullar crista, and endolymphatic sac by using cationic polyethyleneimine (PEI). Furosemide was intravenously administered to albino guinea pigs with normal Preyer's reflexes. After 20 minutes, the bony labyrinth was removed and processed for histologic evaluation. Under a transmission electron microscope, a marked enlargement of the intercellular spaces was observed in the stria vascularis. The PEI distribution decreased significantly on the capillary BL in the stria vascularis and on the subepithelial BL in the sensory, transitional, and dark cell areas. However, no significant change was observed on the capillary BL or the subepithelial BL in the endolymphatic sac. These findings suggest that acute furosemide administration severely alters the distribution of the anionic sites in the strial capillary BL and in the subepithelial BL in the ampullar crista, but not in the capillary BL or the subepithelial BL of the endolymphatic sac.

Expression pattern of the mouse ortholog of the Pendred's syndrome gene (Pds) suggests a key role for pendrin in the inner ear

Pendred's syndrome is an autosomal-recessive disorder characterized by deafness and goiter. After our recent identification of the human gene mutated in Pendred's syndrome (PDS), we sought to investigate in greater detail the expression of the gene and the function of its encoded protein (pendrin). Toward that end, we isolated the corresponding mouse ortholog (Pds) and performed RNA in situ hybridization on mouse inner ears (from 8 days postcoitum to postnatal day 5) to establish the expression pattern of Pds in the developing auditory and vestibular systems. Pds expression was detected throughout the endolymphatic duct and sac, in distinct areas of the utricle and saccule, and in the external sulcus region within the cochlea. This highly discrete expression pattern is unlike that of any other known gene and involves several regions thought to be important for endolymphatic fluid resorption in the inner ear, consistent with the putative functioning of pendrin as an anion transporter. These studies provide key first steps toward defining the precise role of pendrin in inner ear development and elucidating the pathogenic mechanism for the deafness seen in Pendred's syndrome.

Endolymphatic hydrops reduces retrograde labeling of trigeminal innervation to the cochlea

This paper reports that endolymphatic hydrops causes a significant reduction of retrogradely labeled cell bodies of the ipsilateral trigeminal ganglion following application of horseradish peroxidase in the cochlea. We previously showed that the trigeminal ganglion is a source of primary sensory innervation to the cochlear blood vessels. The innervation of the cochlea from the trigeminal ganglion may provide the basis of an alternative mechanism for Ménière's syndrome (imbalance, hearing loss, tinnitus, and a sensation of fullness in the ear) for which a central neural basis has been speculated. Innervation patterns of sensory nerves from the trigeminal ganglion to the cochlear blood vessels were studied using retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Healthy and hydropic guinea pigs were unilaterally implanted with an osmotic pump and a cannula for cochlear delivery of 2% WGA-HRP or vehicle alone. In other guinea pigs the cochlea was pretreated with 100 micromol capsaicin before administering 2% WGA-HRP. Histological sections of the ipsi- and contralateral trigeminal ganglia were obtained 48 h after WGA-HRP infusion. In the hydropic guinea pig, the number of labeled nerve cell bodies observed in the anteriomedial portion of the trigeminal ganglion at the origin of the ophthalmic nerve was reduced by 70% relative to normal animals. Capsaicin pretreatment nearly eliminated the labeled sensory fibers as expected. These data indicate that the trigeminal innervation to the cochlea could be involved in inner ear homeostatic disturbances, including the hydrops that is symptomatic of Ménière's disease.

Fixation-induced shrinkage of Reissner's membrane and its potential influence on the assessment of endolymph volume

The quantification of endolymph volume by histological techniques or by magnetic resonance (MR) microscopy requires the inner ear to be first treated with chemical fixatives. If the fixative induces soft-tissue shrinkage, it would tend to return a distended Reissner's membrane towards a straight position, since this membrane is anchored to bone at its medial and lateral edges. The goal of this study was to determine the degree of Reissner's membrane shrinkage induced by different fixation protocols to establish methods which minimize tissue shrinkage. Fragments of fresh Reissner's membrane were dissected from isolated cochleae in an artificial perilymph. Specimens were viewed with an inverted microscope during infusion of fixatives, and changes recorded on video tape. Size changes of the specimen were quantified, usually over a 20 min period. Heidenhain-Susa, a fixative which is widely used in histological studies of hydropic cochleae, caused substantial shrinkage of Reissner's membrane, decreasing the length of specimens by an average of 15.1%. Other fixation procedures induced far less shrinkage. The use of 3.1% glutaraldehyde in Hanks' balanced salt solution produced a mean length decrease of only 0.3%. The inclusion in the fixation medium of 4.5% mercuric chloride, corresponding to the concentration which is present in Heidenhain-Susa and which acts to increase the contrast of Reissner's membrane in MR microscopy, contributes significantly to specimen shrinkage. We can conclude that the degree of endolymphatic hydrops may be underestimated in specimens fixed with media containing high levels of mercuric chloride.

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.