Monitoring inner ear pressure changes in normal guinea pigs induced by the Meniett20

Monitoring pressure changes in the inner ear induced by middle ear pressure therapy with an EFET01 device in guinea pigs

BACKGROUND

As a low-cost, portable, handheld air pressure generation tool not requiring a ventilation tube, the EFET01 device has shown clinical effectiveness for intractable Ménière's disease (MD) patients in Japan. However, no animal studies have investigated changes in inner ear pressure (PI) when applying this device.

OBJECTIVE

To determine the PI properties in response to middle ear pressure therapy (MEPT) induced by the EFET01 in guinea pigs.

MATERIAL AND METHODS

In seven healthy guinea pigs, bi-phasic pressure pulses from -5 to 12 cm H2O were delivered to the external ear canal and transmitted to the middle and inner ear cavities with an intact tympanic membrane. Hydrostatic pressure change in the inner ear perilymphatic compartment was measured by a servo-controlled micropipette system.

RESULTS

From eight successful ears, pressure changes in the middle ear slightly decreased and were instantly transferred to the inner ear. The EFET01 produces a bi-phasic positive/negative pressure pulse, which is approximately twice as large as the monophasic pressure pulse.

CONCLUSION

Our study clarified the EFET01's ability to transmit pressure and verified its effectiveness in MD patients as observed in clinical studies.

SIGNIFICANCE

The PI properties in guinea pig response to MEPT with the EFET01 device were investigated.

Case Report: Positive Pressure Therapy Combined With Endolymphatic sac Surgery in a Patient With Ménière's Disease

Positive pressure therapy (PPT) is applied for medically-intractable vertigo in Ménière's disease (MD); however, it remains unknown whether PPT affects in vivo endolymphatic hydrops (EH). In this case report, we describe a 5-year course of MD in a patient in which EH was repeatedly observed. As the patient experienced recurrent vertigo attacks after endolymphatic sac surgery, he began to use the PPT device additionally and vertiginous episodes decreased in accordance with a decrease in the EH volume. The mechanism of PPT is suggested that the pressure increase in the middle ear inhibits EH development. PPT, if added after surgery, might be more effective to reduce EH volume compared with surgery alone. A larger study group size is required to test these preliminary data concerning EH changes.

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.

Clinical long-term effects of Meniett pulse generator for Meniere's disease

CONCLUSION

According to this long-term study, the Meniett pulse generator is a safe, effective, and non-destructive therapy that can reduce vertiginous symptoms and associated functional handicap and partly show an improvement of hearing in medically intractable and active Meniere's disease. Moreover, we recommend considering it before attempting any surgical or chemical vestibular ablation procedure.

OBJECTIVE

To evaluate the long-term efficacy and safety of transtympanic pressure treatment in the management of recalcitrant vertigo in Meniere's disease.

PATIENTS AND METHODS

This was a cross-sectional case study of 22 consecutive patients with medically active and intractable Meniere's disease who opted to try the Meniett pulse generator between July 2005 and March 2008. Eighteen of these patients were followed up for over 24 months. A standard ventilation tube was inserted in the affected ear. The treatment period with the Meniett pulse generator was 2 months in clinic, then the follow-up was a mean of 28 months. Patients indicated on the symptom report card and six-point functional scale the maximum level of vertigo, activity, and stress. Hearing was assessed utilizing pure tone average thresholds (PTAs) and the vestibular caloric test was performed.

RESULTS

For 18 patients, the changes on the vertigo visual analog scale (VAS) and six-point functional scale before and after treatment with the Meniett device were statistically significant (p<0.05). No changes in vestibular function were noted. In all, 13 and 10 of 18 patients, respectively, showed a significant PTA increase of 10 dB or more at 2 months and 12 months after treatment with the Meniett device. Nine of 17 patients showed a significant PTA increase of 10 dB or more at 24 months after the treatment. There were no complications during the 28-month follow-up.

Cochlear aqueduct flow resistance depends on round window membrane position in guinea pigs

The resistance for fluid flow of the cochlear aqueduct was measured in guinea pigs for different positions of the round window membrane. These different positions were obtained by applying different constant pressures to the middle ear cavity. Fluid flow through the aqueduct was induced by small pressure steps superimposed on these constant pressures. It was found that the resistance for fluid flow through the aqueduct depended on the round window position but not on flow direction. The results can be explained by special fibrous structures that connect the round window with the entrance of the aqueduct. It was also found that the equilibrium inner ear pressure depends on middle ear pressure, indicating that the aqueduct does not connect the inner ear with a cavity with constant pressure.

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.

Cochlear aqueduct flow resistance is not constant during evoked inner ear pressure change in the guinea pig

Inner ear fluid pressure was measured during 6.25 mHz square wave middle ear pressure manipulation, with a perforated tympanic membrane. After a negative-going middle ear pressure change the calculated flow resistance of the inner ear pressure release routes (mainly the cochlear aqueduct) was approximately constant, with a value of 12 Pa s/nl (averaged over two ears), when values for the inner ear window compliance are taken from the literature. After a positive-going middle ear pressure change the calculated flow resistance changed with round window position and with the pressure difference across the cochlear aqueduct. It reached an average maximum value of 114 Pa s/nl. The change of flow resistance during inner ear pressure variation can be explained by a permeability change of the cochlear aqueduct, caused by a change of structures filling the aqueduct and its entrance in scala tympani.

Change of guinea pig inner ear pressure by square wave middle ear cavity pressure variation

The inner ear fluid pressure of guinea pigs was measured during square wave middle ear cavity pressure variation. Time constants were derived for the slopes of the inner ear pressure recovery curves after middle ear pressure change. A "single exponential" function did not fit well and therefore more complicated functions were used for this purpose. For middle ear pressure increasing from zero to a few centimetres of water, returning to zero again, decreasing from zero to minus a few centimetres of water and then returning to zero again, time constants for the inner ear pressure recovery curves were on average 15.0, 8.6, 2.5 and 2.5 s, respectively. The results could not be described using a linear model with constant window membrane compliance and cochlear aqueduct flow resistance. A possible explanation for the large difference in time constants for positive or negative middle ear pressure changes is a dependence on aqueduct flow resistance or round window membrane position.