Interinterpreter variability in determining the SP/AP ratio in clinical electrocochleography

Tone burst electrocochleography disproves a diagnosis of Meniere's disease treated aggressively

Reliable confirmation of the presence or absence of endolymphatic hydrops is essential to avoid confusing vestibular migraine with Meniere's disease. MRI inner ear imaging is a promising new method to confirm hydrops, avoiding both unnecessary invasive or destructive inner ear treatments, but it is not universally available. Tone burst electrocochleography is an older simple, quick, safe, and sensitive test that is potentially available, with existing (or minorly upgraded) equipment at most tertiary medical centers. In Meniere's disease hydrops remains after intratympanic treatments. A case is presented of a 45 year-old man with a long history of recurrent vertigo attacks who, due to an erroneous diagnosis of Meniere's disease, was given five intratympanic treatments with no effect. He was subsequently found by tone burst electrocochleography to have no hydrops and was differentially diagnosed with probable vestibular migraine. Response to treatment confirms this diagnosis. This patient's electrocochleographic findings are compared with two other patients with definite Meniere's disease, one of whom had demonstrable hydrops despite intratympanic gentamycin treatments.

Management of Far-Advanced Otosclerosis: Stapes Surgery or Cochlear Implant

Objective

The aim of this report is to share our experience and treatment outcomes with far-advanced otosclerosis (FAO) patients.

Methods

Patients that underwent surgery from 2003 through 2014 at a tertiary referral center were retrospectively reviewed. Nineteen FAO patients were included in the study. Audiological results and the ability to communicate face to face and over telephone were considered as the main outcome measures.

Results

Six FAO patients benefited well from stapedotomy with an average of 5.9-decibel (dB) air-bone gap and 86% median speech discrimination. Cochlear implantation (CI) was performed in 13 patients; two had disease progression after stapedotomy, five had failed stapes surgeries elsewhere, and six preferred CI as primary treatment. Median speech discrimination score of CI patients was 78.4%. Overall, all patients had satisfactory face-to-face communication and 90% could use telephone.

Conclusion

Bilateral stapedotomy and wearing hearing aid is an effective and cost-effective solution for restoring natural binaural hearing and requires no specific training. Should stapedotomy fail, cochlear implantation is always a successful back-up option.

Hidden Hearing Loss? No Effect of Common Recreational Noise Exposure on Cochlear Nerve Response Amplitude in Humans

This study tested hypothesized relationships between noise exposure and auditory deficits. Both retrospective assessment of potential associations between noise exposure history and performance on an audiologic test battery and prospective assessment of potential changes in performance after new recreational noise exposure were completed.

Methods: 32 participants (13M, 19F) with normal hearing (25-dB HL or better, 0.25–8 kHz) were asked to participate in 3 pre- and post-exposure sessions including: otoscopy, tympanometry, distortion product otoacoustic emissions (DPOAEs) (f2 frequencies 1–8 kHz), pure-tone audiometry (0.25–8 kHz), Words-in-Noise (WIN) test, and electrocochleography (eCochG) measurements at 70, 80, and 90-dB nHL (click and 2–4 kHz tone-bursts). The first session was used to collect baseline data, the second session was collected the day after a loud recreational event, and the third session was collected 1-week later. Of the 32 participants, 26 completed all 3 sessions.

Results: The retrospective analysis did not reveal statistically significant relationships between noise exposure history and any auditory deficits. The day after new exposure, there was a statistically significant correlation between noise “dose” and WIN performance overall, and within the 4-dB signal-to-babble ratio. In contrast, there were no statistically significant correlations between noise dose and changes in threshold, DPOAE amplitude, or AP amplitude the day after new noise exposure. Additional analyses revealed a statistically significant relationship between TTS and DPOAE amplitude at 6 kHz, with temporarily decreased DPOAE amplitude observed with increasing TTS.

Conclusions: There was no evidence of auditory deficits as a function of previous noise exposure history, and no permanent changes in audiometric, electrophysiologic, or functional measures after new recreational noise exposure. There were very few participants with TTS the day after exposure - a test time selected to be consistent with previous animal studies. The largest observed TTS was approximately 20-dB. The observed pattern of small TTS suggests little risk of synaptopathy from common recreational noise exposure, and that we should not expect to observe changes in evoked potentials for this reason. No such changes were observed in this study. These data do not support suggestions that common, recreational noise exposure is likely to result in “hidden hearing loss”.

Tone Burst Electrocochleography for the Diagnosis of Clinically Certain Meniere's Disease

The technique of transtympanic electrocochleography was initially developed as an objective hearing threshold test by Eggermont. Gibson et al. (1977) claimed that an enlarged direct current component of the action potential (AP) called the summating potential (SP) is an indication of endolymphatic hydrops, later confirmed by Coates who proposed an SP/AP ratio measure. This led to numerous publications using diagnostic ratios of 0.33-0.35. The insensitivity led to an eventual disenchantment with the test as a reliable objective test for Meniere's disease. It was further confused by audiologists employing remote canal or ear drum electrodes which give a response about one-fourth of the magnitude obtained by an electrode in contact with the cochlea. Subsequently Gibson stated that an SP/AP ratio of <0.5 is not diagnostic for hydrops. He then showed that a tone burst stimulus gave the test a significantly higher sensitivity and specificity, which has been supported by others. On MRI inner ear imaging with gadolinium hydrops can be seen, but the quality of images and what is seen may vary according to brand of scanner, settings, mode of gadolinium administration, and the possibility that gadolinium entry may favor the vestibule. Transtympanic tone burst electrocochleography is to date the simplest, cheapest and most sensitive technique for detecting cochlear endolymphatic hydrops to confirm a diagnosis of Meniere's disease.

Quality of perioperative AEP—variability of expert ratings

BACKGROUND

Previous studies suggest that auditory evoked potentials (AEP) may be used to monitor anaesthetic depth. However, during surgery and anaesthesia, the quality of AEP recordings may be reduced by artefacts. This can affect the interpretation of the data and complicate the use of the method. We assessed differences in expert ratings of the signal quality of perioperatively recorded AEPs.

METHODS

Signal quality of 180 randomly selected AEP, recorded perioperatively during a European multicentre study, was rated independently by five experts as 'invalid' (0), 'poor' (1), or 'good' (2). Average (n=5) quality rating was calculated for each signal. Differences between quality ratings of the five experts were calculated for each AEP: inter-rater variability (IRV) was calculated as the difference between the worst and best classification of a signal.

RESULTS

Average signal quality of 57% of the AEPs was rated as 'invalid', 39% as 'poor', and only 4% as 'good'. IRV was 0 in only 6%, 1 in 62%, and 2 in 32% of the AEP, that is in 32% one expert said signal quality was good, whereas a different expert thought the identical signal was invalid.

CONCLUSIONS

There is poor agreement between experts regarding the signal quality of perioperatively recorded AEPs and, as a consequence, results obtained by one expert may not easily be reproduced by a different expert. This limits the use of visual AEP analysis to indicate anaesthetic depth and may affect the comparability of AEP studies, where waveforms were analysed by different experts. An objective automated method for AEP analysis could solve this problem.

Summating potential & summating potential/action potential ratio in the diagnosis of Meniere's disease

This study assesses electrocochleographic (ECOG) potentials in a clinically defined Meniere's group and compares the results with those from a normal control group. Electrocochleography was done in 42 cases of Meniere's disease and was compared with 20 normal cases. All parameters of electrocochleography were studied with special emphasis on the summating potential/action potential (SP/AP) ratio. A SP/AP amplitude ratio of 0.49 was found in the Meniere' group as compared to the SP/AP ratio of 0.03 in the control group. Latencies of SP and AP were also studied and compared between two groups.