Local Pressure Protocol, Including Meniett, in the Treatment of Me´nie`re's Disease: Short-term Results During the Active Stage

Positive pressure therapy for Ménière's disease

BACKGROUND

Ménière's disease is a condition that causes recurrent episodes of vertigo, associated with hearing loss and tinnitus. It is often treated with medication, but different interventions are sometimes used. Positive pressure therapy is a treatment that creates small pressure pulses, generated by a pump that is attached to tubing placed in the ear canal. It is typically used for a few minutes, several times per day. The underlying cause of Ménière's disease is unknown, as is the way in which this treatment may work. The efficacy of this intervention at preventing vertigo attacks, and their associated symptoms, is currently unclear.

OBJECTIVES

To evaluate the benefits and harms of positive pressure therapy versus placebo or no treatment in people with Ménière's disease.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Register; CENTRAL; Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 14 September 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs in adults with a diagnosis of Ménière's disease comparing positive pressure therapy with either placebo or no treatment. We excluded studies with follow-up of less than three months.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were: 1) improvement in vertigo (assessed as a dichotomous outcome - improved or not improved), 2) change in vertigo (assessed as a continuous outcome, with a score on a numerical scale) and 3) serious adverse events. Our secondary outcomes were: 4) disease-specific health-related quality of life, 5) change in hearing, 6) change in tinnitus and 7) other adverse effects. We considered outcomes reported at three time points: 3 to < 6 months, 6 to ≤ 12 months and > 12 months. We used GRADE to assess the certainty of evidence for each outcome.  MAIN RESULTS: We included three studies with a total of 238 participants, all of which compared positive pressure using the Meniett device to sham treatment. The duration of follow-up was a maximum of four months.  Improvement in vertigo A single study assessed whether participants had an improvement in the frequency of their vertigo whilst using positive pressure therapy, therefore we are unable to draw meaningful conclusions from the results.  Change in vertigo Only one study reported on the change in vertigo symptoms using a global score (at 3 to < 6 months), so we are again unable to draw meaningful conclusions from the numerical results. All three studies reported on the change in the frequency of vertigo. The summary effect showed that people receiving positive pressure therapy had, on average, 0.84 fewer days per month affected by vertigo (95% confidence interval from 2.12 days fewer to 0.45 days more; 3 studies; 202 participants). However, the evidence on the change in vertigo frequency was of very low certainty, therefore there is great uncertainty in this estimate.   Serious adverse events None of the included studies provided information on the number of people who experienced serious adverse events. It is unclear whether this is because no adverse events occurred, or whether they were not assessed and reported.  AUTHORS' CONCLUSIONS: The evidence for positive pressure therapy for Ménière's disease is very uncertain. There are few RCTs that compare this intervention to placebo or no treatment, and the evidence that is currently available from these studies is of low or very low certainty. This means that we have very low confidence that the effects reported are accurate estimates of the true effect of these interventions. Consensus on the appropriate outcomes to measure in studies of Ménière's disease is needed (i.e. a core outcome set) in order to guide future studies in this area and enable meta-analyses of the results. This must include appropriate consideration of the potential harms of treatment, as well as the benefits.

Association between Meniere's disease and air pollution in South Korea

Meniere's disease is thought to be a disorder of the inner ear function, affected by genetic and environmental factors. Several recent studies have shown that air pollution could affect middle and inner ear diseases. The purpose of this study was to investigate the relationship between the Meniere's disease occurrence and air pollution status in Korea. This study used a time-stratified case-crossover design. Hospital visit data by Meniere's disease were collected from the Korea National Health Insurance Service-National Sample Cohort (NHIS-NSC) database. Daily air pollution data for sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), and particulate matter (PM10: ≤ 10 μm in diameter, and PM2.5: ≤ 2.5 μm in diameter) were collected from the National Ambient air quality Monitoring Information System (NAMIS) database. We used two-stage analysis to assess the association between degree of air pollution and the occurrence of Meniere's disease. In the first stage, region-specific analysis was conducted to estimate the odds ratios (ORs) of Meniere's disease risk associated with each air pollutant exposure by using conditional logistic regression for matched case-control sets in 16 regions. In the second stage, region-specific ORs from the first stage were combined and the pooled effect estimates were derived through fixed and random effect meta-analysis. Subgroup analysis was conducted for age, sex, seasonality, and urbanization of residence. In total, 29,646 (32.1% males and 67.9% females) Meniere's disease cases were identified from Korea NHIS-NSC database between 2008 and 2015. Overall, SO2, NO2, CO, and PM10 showed significant correlation with Meniere's disease risk at immediate lags, and weaker correlation at delayed lags, whereas O3 showed slightly negative correlation at the immediate lag (lag0) and PM2.5 did not show strong correlation (SO2: 1.04 [95% confidence interval: 1.01, 1.06]; NO2: 1.08 [1.06, 1.11]; CO: 1.04 [1.02, 1.06]; O3: 0.96 [0.93, 0.99]: statistically significant ORs at lag0 are listed). These positive and negative associations between Meniere's disease and each air pollutant were generally stronger in the age of 40-64, female, summer (June-August) season, and urban subgroups. Our results showed that hospital visits for Meniere's disease were associated with the measured concentrations of ambient air pollutants SO2, NO2, CO, and PM10. Further studies are required to confirm these associations and find their mechanisms.

Vertiginous Episodes in Menière Disease following Transmyringeal Ventilation Tube Insertion: A Systematic Review on the Current State of Evidence

Introduction  Menière disease (MD) is a disorder characterized by episodes of vertigo, sensorineural hearing loss, tinnitus and aural fullness. Objectives  To assess the effect of ventilation tube insertion (VTI) on vertiginous episodes in patients (≥ 18 years old) with MD. Data Synthesis  A systematic literature search on randomized clinical trials (RCTs), nonrandomized trials and other systematic reviews was performed. The Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach was used to assess the overall certainty of evidence. Two RCTs and four nonrandomized studies were identified. Data extraction was only possible for one RCT. Results showed that the number of patients with no vertigo attacks significantly increased following active treatment (relative risk 1.52; [95% confidence interval: 1.19-1.94]). The quality of evidence was rated as low. None of the nonrandomized trials included a proper control group, which hindered data extraction and quality assessment. Conclusion  There are currently no RCTs that specifically assess the efficacy of VTI in patients with MD. Current limited data suggest a considerable positive effect on the number of vertiginous episodes in patients with MD. However, due to poor evidence, a fluctuating course and a substantial placebo-effect associated with MD-treatment, no solid conclusion(s) regarding the efficacy of VTI can be made. There is a need for high-quality RCTs.

Meniett device in meniere disease: Randomized, double-blind, placebo-controlled multicenter trial

OBJECTIVE

To evaluate the efficacy of portable Meniett low-pressure pulse generator (Medtronic Xomed, Jacksonville, FL) in Meniere disease.

STUDY DESIGN

Randomized, double-blind, placebo-controlled, multicenter trial carried out in 17 academic medical centers.

METHODS

One hundred twenty-nine adults presenting Meniere disease (American Academy of Otolaryngology-Head and Neck Surgery criteria) not controlled by conventional medical treatment were included. The protocol included three phases: 1) placement of a transtympanic tube and evaluation of its effect (if resolution of symptoms, the patient was excluded); 2) randomization: 6-weeks treatment with Meniett (Medtronic Xomed) or placebo device; 3) removal of the device and 6-week follow-up period. The evaluation criteria were the number of vertigo episodes (at least 20 minutes with a 12-hour free interval) and the impact on daily life as assessed by self-questionnaires.

RESULTS

Ninety-seven patients passed to the second phase of the study: 49 and 48 patients received the Meniett (Medtronic Xomed) or the placebo device, respectively. In the placebo group, the number of vertigo episodes decreased from 4.3 ± 0.6 (mean ± standard error of the mean) during the first phase to 2.6 ± 0.5 after 6 weeks of treatment, and to 1.8 ± 0.8 after the removal of the device. Similar results were observed in the Meniett device (Medtronic Xomed) group: 3.2 ± 0.4 episodes during the first phase, 2.5 ± after 6 weeks of Meniett device (Medtronic Xomed) treatment, and 1.5 ± 0.2 after the third phase.

CONCLUSION

An improvement of symptoms was evidenced in all patients, with no difference between the Meniett (Medtronic Xomed) and the placebo device groups. The decrease in the number of vertigo episodes could be explained by an effect of the medical care.

LEVEL OF EVIDENCE

1b. Laryngoscope, 2016 127:470-475, 2017.

Positive pressure therapy for Ménière's disease or syndrome

BACKGROUND

Ménière's disease is an incapacitating disease in which recurrent attacks of vertigo are accompanied by hearing loss, tinnitus and/or aural fullness, all of which are discontinuous and variable in intensity. A number of different therapies have been identified for patients with this disease, ranging from dietary measures (e.g. a low-salt diet) and medication (e.g. betahistine (Serc®), diuretics) to extensive surgery (e.g. endolymphatic sac surgery). The Meniett® low-pressure pulse generator (Medtronic ENT, 1999) is a device that is designed to generate a computer-controlled sequence of low-pressure (micro-pressure) pulses, which are thought to be transmitted to the vestibular system of the inner ear. The pressure pulse passes via a tympanostomy tube (grommet) to the middle ear, and hence to the inner ear via the round and/or oval window. The hypothesis is that these low-pressure pulses reduce endolymphatic hydrops.

OBJECTIVES

To assess the effects of positive pressure therapy (e.g. the Meniett device) on the symptoms of Ménière's disease or syndrome.

SEARCH METHODS

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the search was 6 June 2014.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing positive pressure therapy (using the Meniett or a similar device) with placebo in patients with Ménière's disease. The primary outcome was control of vertigo; secondary outcomes were loss or gain of hearing, severity of tinnitus, perception of aural fullness, functional level, complications or adverse effects, and sick days.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies, assessed risk of bias and extracted data. We contacted authors for additional data. Where possible, we pooled study results using a fixed-effect, mean difference (MD) meta-analysis and tested for statistical heterogeneity using both the Chi² test and I² statistic. This was only possible for the secondary outcomes loss or gain of hearing and sick days. We presented results using forest plots with 95% confidence intervals (Cl).

MAIN RESULTS

We included five randomised clinical trials with 265 participants. All trials were prospective, double-blind, placebo-controlled randomised controlled trials on the effects of positive pressure therapy on vertigo complaints in Ménière's disease. Overall, the risk of bias varied: three out of five studies were at low risk, one was at unclear risk and one was at high risk of bias. Control of vertigo For the primary outcome, control of vertigo, it was not possible to pool data due to heterogeneity in the measurement of the outcome measures. In most studies, no significant difference was found between the positive pressure therapy group and the placebo group in vertigo scores or vertigo days. Only one study, at low risk of bias, showed a significant difference in one measure of vertigo control in favour of positive pressure therapy. In this study, the mean visual analogue scale (VAS) score for vertigo after eight weeks of treatment was 25.5 in the positive pressure therapy group and 46.6 in the placebo group (mean difference (MD) -21.10, 95% CI -35.47 to -6.73; scale not stated - presumed to be 0 to 100). Secondary outcomes For the secondary outcomes, we carried out two pooled analyses. We found statistically significant results for loss or gain of hearing . Hearing was 7.38 decibels better in the placebo group compared to the positive pressure therapy group (MD) (95% CI 2.51 to 12.25; two studies, 123 participants). The severity of tinnitus and perception of aural fullness were either not measured or inadequate data were provided in the included studies. For the secondary outcome functional level , it was not possible to perform a pooled analysis. One included study showed less functional impairment in the positive pressure group than the placebo group (AAO-HNS criteria, one- to six-point scale: MD -1.10, 95% CI -1.81 to -0.39, 40 participants); another study did not show any significant results. In addition to the predefined secondary outcome measures, we included sick days as an additional outcome measure, as two studies used this outcome measure and it is a complementary measurement of impairment due to Ménière's disease. We did not find a statistically significant difference in sick days. No complications or adverse effects were noted by any study.

AUTHORS' CONCLUSIONS

There is no evidence, from five included studies, to show that positive pressure therapy is effective for the symptoms of Ménière's disease. There is some moderate quality evidence, from two studies, that hearing levels are worse in patients who use this therapy. The positive pressure therapy device itself is minimally invasive. However, in order to use it, a tympanostomy tube (grommet) needs to be inserted, with the associated risks. These include the risks of anaesthesia, the general risks of any surgery and the specific risks of otorrhoea and tympanosclerosis associated with the insertion of a tympanostomy tube. Notwithstanding these comments, no complications or adverse effects were noted in any of the included studies.

Systematic review and meta-analysis of Meniett therapy for Meniere's disease

OBJECTIVES/HYPOTHESIS

To perform a systematic review and meta-analysis of micropressure treatment for Meniere's disease (MD).

DATA SOURCES

Medline, Ovid, Web of Science, and Cochrane Library search of the literature from January 1996 to December 2012.

REVIEW METHODS

Systematic literature review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Inclusion criteria required definitive diagnosis of unilateral MD, treatment with Meniett device, vertigo control results, and hearing results before and after treatment. Randomized controlled trials and other types of case-control studies were included. Improvements in vertigo, American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) functional score, and pure tone average (PTA) were assessed. Funnel plots were used to detect bias and Q test was used to assess for heterogeneity. Random effects model was used for meta-analysis. T test was used to assess for significance.

RESULTS

Of 113 abstracts screened, 18 studies met criteria for review and 12 were used for meta-analysis. Eight studies reported hearing evaluation and the improvement in PTA after Meniett treatment was significant (P = 0.0085). Data could not be combined for AAO-HNS functional score due to heterogeneity. However, there was a trend toward improvement. Of six studies reporting frequency of vertigo, Meniett treatment significantly reduced frequency of vertigo (P = < .0001).

LIMITATIONS

Much of the data used in the analysis was derived from retrospective or level 4 studies. The average follow-up was only 5 months, and there were low number of patients in the treatment and control groups.

CONCLUSION

The Meniett device is a safe, nondestructive treatment for patients' refractory to medical therapy for MD.

Meniett device for Ménière's disease: use and compliance at 3 to 5 years

OBJECTIVE

To review the continued use of the Meniett device 2 and 3 years after the device's initial prescription.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

PATIENTS

Patients fitting American Academy of Otolaryngology-Head and Neck Surgery criteria for Ménière's disease who had failed conventional medical therapy between February 2002 and April 2004 and who were ready for surgical intervention.

INTERVENTION

Patients used the Meniett device as a nonsurgical alternative for Ménière's management.

OUTCOME MEASURES

Continued use or non-use of the device.

RESULTS

Twenty-three patients were prescribed and obtained the Meniett device in the study interval. At 2 years of minimum follow-up, there were 21 evaluable patients. Eleven patients (52%) continued to use the device and have good control of vertiginous symptoms at 2+ years. Four patients (19%) were asymptomatic at 1 year and discontinued the use of the device. Six patients (29%) had no impact on their Ménière's symptoms and stopped using the device within the first 3 months. At 3 years of minimum follow-up, there were 19 evaluable patients; of whom, 63% were either using the device or had become asymptomatic. No complications were attributable to the device.

CONCLUSION

We conclude that the Meniett device is a useful minimally invasive alternative in the management of Ménière's disease. Among these patients who had failed previous medical management, 71% and 63% required no additional intervention beyond the Meniett device at a minimum of 2 and 3 years of follow-up, respectively. Most patients who failed to gain benefit did so early on in therapy.

Meniett therapy may avoid vestibular neurectomy in disabling Meniere's disease

CONCLUSION

In those patients for whom vestibular neurectomy has been selected due to the disabling recurrence of vertigo spells, Meniett therapy has been shown to allow avoidance of this surgical procedure in a fairly high percentage of patients with Meniere's disease (MD). Our data would also support a better result when pressure treatment is acting on MD of short duration.

OBJECTIVE

To test the possibility that low pressure treatment (Meniett) could avoid vestibular neurectomy in patients with MD that was refractory to medical treatment.

PATIENTS AND METHODS

The setting was a tertiary referral centre in a university hospital. Thirty-six MD patients, for whom vestibular neurectomy was indicated, underwent Meniett treatment and composed a group in which a long-term (>2 years) follow-up was achieved. Additionally, different durations of MD ('young' and 'old' MD) were distinguished and analysed separately.

RESULTS

Twenty-five patients (69.4%) were treated satisfactorily by using Meniett treatment and therefore avoided vestibular neurectomy. In half of them only one cycle of treatment was necessary.

Functional outcome of treatment of Ménière's disease with the Meniett pressure generator

CONCLUSION

Use of the Meniett pressure generator in patients with active Ménière's disease (MD) did not affect labyrinthine function.

OBJECTIVE

To investigate whether application of the Meniett pressure generator in patients with active MD significantly affects their labyrinthine function.

MATERIAL AND METHODS

We measured hearing and labyrinth sensitivity in patients with established MD according to American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) criteria at five different time periods: at baseline; before ventilation tube placement; before Meniett treatment; immediately after Meniett treatment; and 1 month after cessation of Meniett treatment.

RESULTS

A total of 32 patients met the inclusion criteria and were included in the study. They were graded as having definite MD (AAO-HNS stages 2 and 3). No statistically significant changes in labyrinthine function were found during Meniett treatment.

Meniett therapy: rescue treatment in severe drug-resistant Ménière's disease?

CONCLUSION

Our data indicate that Meniett therapy is unlikely to be helpful in the long-term treatment of patients with severe, drug-resistant Ménière's disease (MD) in whom injection of intratympanic gentamicin (ITG) or another destructive procedure would otherwise be performed.

OBJECTIVE

To investigate the value of Meniett therapy in patients with drug-resistant MD referred for injection of ITG.

MATERIAL AND METHODS

Twelve patients referred for ITG treatment were followed during a 2-month period of Meniett therapy. Symptoms, functional level and hearing status were evaluated using a standardized staging system. Disease-specific quality-of-life measures were obtained before and after Meniett therapy. At the end of the study period, patients were followed for a mean of 37 months, thus providing long-term outcome data.

RESULTS

In two patients, Meniett treatment was interrupted after 1 month because of persistent severe vertigo. In the remaining 10 subjects, we found a significant decrease in the median number of vertigo spells from 10.0/month (25th-75th percentile 4.0-19.0) prior to treatment to 3.0/month (25th-75th percentile 1.5-4.5) after treatment (p = 0.02). There was, however, no improvement in hearing status, tinnitus, functional level or self-perceived dizziness handicap. Long-term (>1 year) follow-up data revealed that only 2 subjects preferred to continue Meniett therapy and that ablative surgery had to be performed in 6/12 study patients.

Effects of hyperbaric therapy on function and morphology of Guinea pig cochlea with endolymphatic hydrops

OBJECTIVE

The objective of this study was to investigate the effect on experimental endolymphatic hydrops in guinea pigs after hyperbaric therapy.

BACKGROUND

The histopathologic character of Ménière's disease is the presence of endolymphatic hydrops. Endolymphatic hypertension could be one of the factors resulting from endolymphatic hydrops. Some treatments of Ménière's disease are aimed toward preventing the endolymphatic hypertension. Exposure to pressure change has risen in recent years.

METHODS

Thirty-two guinea pigs were operated on the right ears to induce endolymphatic hydrops by obliterating the endolymphatic sac through an extradural posterior cranial fossa approach. After 5 weeks' survival, 12 guinea pigs were put into a chamber with an absolute atmospheric pressure of 2.2 for 3 weeks (90 minutes once a day 5 times a week). We observed the morphologic and functional changes in guinea pig cochleae of the pressure group, 4-week hydrops group (n = 10), 8-week hydrops group (n = 10), and the normal group (n = 10). We measured the hearing threshold of the auditory brainstem response, the 70-dB SPL action potential (AP) latency, the ratio of 70-dB SPL summating potential magnitude to action potential magnitude (-SP/AP) of the electrocochleogram, and the maximum scala media area (SMA) ratio, respectively.

RESULTS

The average 70-dB SPL-SP/AP magnitude of right ears (0.29 +/- 0.09) and the average maximum SMA ratio (2.23 +/- 0.20) in the pressure group were significantly less than that in the 8-week hydrops group (0.69 +/- 0.15 and 4.04 +/- 0.52, respectively) with the same survival time (p < 0.05). The results in the pressure group were almost as similar as that in the 4-week hydrops group (0.29 +/- 0.13 and 2.22 +/- 0.20, respectively) (p > 0.05). The average hearing threshold of ABR of right ears in the pressure group (36.67 +/- 14.30-dB SPL) was lower than that of the 8-week hydrops group (44 +/-1 4.30-dB SPL), but the difference was insignificant (p > 0.05). The average 70-dB SPL AP latency of right ears in the pressure group was not significantly different from those of the 8-week hydrops group, the 4-week hydrops group, or the normal group (p > 0.05).

CONCLUSIONS

Our findings suggest hyperbaric therapy can significantly suppress the development of endolymphatic hydrops and improve cochlear function in guinea pigs. This study provided strong evidence for the development of pressure treatment of Ménière's disease without destroying the inner ear.

Local Overpressure Treatment Reduces Vestibular Symptoms in Patients with M??ni??re's Disease: A Clinical, Randomized, Multicenter, Double-Blind, Placebo-Controlled Study

OBJECTIVES

To evaluate the efficacy of a new device, the Meniett, in the treatment of Meniere's disease. The device delivers pressure pulses to the middle ear through a ventilating tube in the tympanic membrane at a frequency of 6 Hz for 0.6 second. After rising to a pressure level of 1.2 kPa, the pressure oscillates between 0.4 and 1.2 kPa. It is believed that the pressure changes are conveyed to the inner ear, inducing a transport of fluids via the pressure outlets and thus reducing the endolymphatic hydrops.

STUDY DESIGN

A clinical, randomized, multicenter, double-blind, placebo-controlled study. A total of 40 patients were included that had active Meniere's disease according to American Academy of Otolaryngology-Head and Neck Surgery criteria, aged between 20 and 65 years, with a history of at least eight attacks during the past year. After insertion of the ventilation tube, the patients should have had attacks of vertigo for 2 months before entering the study.

OUTCOME MEASURES

Primary study endpoints were change in frequency of vertigo, change of functionality profile, and change in patient perception of vertigo (visual analogue scale); secondary endpoints were perception of tinnitus, aural pressure, and hearing, as well as an audiologic evaluation of hearing before and after the treatment period.

RESULTS

The functionality level improved statistically significantly in the active group compared with the placebo group (p=0.0014), as did the visual analogue scale evaluation of vertigo (p=0.005). There was a trend toward a reduction of the frequency of vertiginous attacks that was not significant (p=0.090). With regard to the secondary endpoints, there was no statistical difference between active and placebo groups.

CONCLUSION

Local overpressure treatment is a novel treatment that is noninvasive, nondestructive, and safe. It significantly reduces vestibular symptoms in patients with Meniere's disease. The Meniett was cleared by the Food and Drug Administration in 2000.

Responses of the endolymphatic sac to perilymphatic injections and withdrawals: evidence for the presence of a one-way valve

Although the endolymphatic sac (ES) is thought to be a primary site for endolymph volume regulation, we have limited knowledge of how it responds to volume and pressure changes. In a prior publication, we demonstrated changes of K(+), Na(+) and endolymphatic sac potential (ESP) resulting from volume injections into, and withdrawals from, scala media of the cochlea. In the present study, we compared the influence of injections into and withdrawals from scala tympani of the cochlea on the endolymphatic sac. It is assumed that similar pressure changes are induced in endolymph and perilymph of both the cochlear and vestibular compartments of the ear. Pressure changes induced by the perilymphatic injections and withdrawals did not induce similar K(+) changes in the ES. The majority of perilymph withdrawals caused K(+) and ESP reductions in the sac, but few injections caused any measurable changes in the sac. Pressure measurements from the ES demonstrated that transmission of labyrinthine pressures to the lumen was directionally sensitive, with negative pressure transmitted more effectively than positive. In other experiments, application of infrasonic stimulation to the ear canal resulted in K(+) increase in the ES. These physiological measurements suggest that the endolymphatic duct may be closed by sustained positive pressure in the vestibule but open during pressure fluctuations. Study of the anatomy where the endolymphatic duct enters the vestibule suggests that the membranous sinus of the endolymphatic duct could act as a mechanical valve, limiting the flow of endolymph from the saccule to the endolymphatic sac when pressure is applied. This structure could therefore play an important role in endolymph volume regulation.