Results of Electrocochleography in Ménière’s Disease after Successful Vertigo Control by Single Intratympanic Gentamicin Injection

Abstract

In the last several years, a promising new approach has been suggested in the therapy of Ménière’s disease (MD): the low-dose intratympanic gentamicin therapy. By titrating the desired vestibular inhibition by single injections and infrequent administration, side effects concerning hearing can be held on an acceptably low level, while disease-related symptoms are often successfully eliminated. However, it is still unclear if endolymphatic hydrops actually decreases when the patients become symptom free. In the literature, hydrops is significantly associated with an enhanced ratio of summating potential/action potential (SP/AP). Our aim in this retrospective study was to answer the question if pathologically high SP/AP ratios normalize after successful low-dose intratympanic gentamicin treatment. Twenty-eight patients with MD received one, two or three intratympanic gentamicin injections. These injections inhibited vertigo spells without causing additional hearing loss. SP/AP ratios measured by noninvasive electrocochleography did not improve statistically when patients became symptom free. This indicates that the beneficial effect of gentamicin does not depend on the improvement of SP/AP ratios. Considering the well-established correlation between increased SP/AP and active MD, it thus seems unlikely that gentamicin treatment significantly reduces hydrops.

Preclinical and Clinical Studies of Unrelieved Aural Fullness following Intratympanic Gentamicin Injection in Patients with Intractable Ménière's Disease

“…However, little is known about the effect of gentamicin upon the function of transitional cells, which merits further study. This hypothesis is supported by the recent MRI study by Fiorino [2012] and electrocochleography results [Büki et al, 2011]. …”

“…In the past few years, alternative measurements of endolymphatic hydrops have been tried in clinical practice, such as MRI scanning and electrocochleography [Büki et al, 2011; Fiorino et al, 2012]. A 3D-FLAIR sequence in 3 T MRI units, after intratympanic gadolinium administration had been used to visualize endolymphatic hydrops indirectly, relying on the imaging of the enlarged space occupied by nongadolinium-enhanced fluid space, reduced the area/volume of the gadolinium-enhanced perilymphatic compartments [Nakashima et al, 2007; Naganawa et al, 2011].…”

“…Ferraro et al [1999] and Devaiah et al [2003] reported that the SP/AP area curve ratio in extratympanic electrocochleography significantly improved the diagnostic sensitivity for endolymphatic hydrops in comparison with conventional SP/AP amplitude ratio in MD [Ferraro and Tibbils, 1999; Devaiah et al, 2003]. Buki et al [2011] proved that SP/AP ratios did not improve statistically even after patients had become symptom free, thus leading to the assumption that the beneficial effect of gentamicin seems more likely to depend on a reduction in the sensitivity of the vestibular periphery, rather than the improvement of endolymphatic hydrops. However, further studies evaluating the diagnostic sensitivity and specificity of the SP/AP area ratio together with the SP/AP amplitude area and other methods, such as vestibular-evoked myogenic potentials, the caloric test or the glycerol test, should still be conducted to increase the sensitivity of early diagnosis of MD and endolymphatic hydrops.…”

“…Furthermore, a recent study revealed no evidence of reduced endolymphatic hydrops following intratympanic gentamicin treatment while using a 3-dimensional fluid-attenuated inversion recovery (3D-FLAIR) sequence in 3-tesla (3 T) MRI units to evaluate endolymphatic hydrops [Fiorino et al, 2012]. In addition, another study measured summating potential/action potential (SP/AP) ratios by noninvasive electrocochleography, which is associated with the degree of endolymphatic hydrops [Yamamoto et al, 2010], and reported that endolymphatic hydrops did not improve statistically even as vertigo was well-controlled following intratympanic gentamicin administration [Büki et al, 2011]. …”

Electrocochleography for Ménière's disease: is it reliable?

“…The elevation of SP amplitude in ears with endolymphatic hydrops appears to depend mainly on the mechanoelectrical transduction process into the cochlea, due to the loss of hair cells or to potassium poisoning of the perilymph, instead of the mechanical factor of the displacement of the basilar membrane. 22 Moon et al noted that patients with abnormal SP/AP exhibited significant elevation in their hearing thresholds compared with those who had SP/AP within the normal range, suggesting that MD patients with severe endolymphatic hydrops suffer more severe hearing deterioration over time 23 ---data corroborated by Ge et al 23 Lopes assessed the sensitivity and specificity of SP/AP ratio and the graphic angular measure in electrocochleography studies of 71 ears (41 MD patients and 14 healthy controls). This author concluded that the graphic angular measure is not sensitive and specific enough for the diagnosis of MD.…”