How reliable is visual assessment of the electrically elicited stapedius reflex threshold during cochlear implant surgery, compared with tympanometry?

Automated detection of electrically evoked stapedius reflexes (eSR) during cochlear implantation

Introduction

In cochlear implantation, objective fitting methods are needed to optimize audiological results in small children or patients with poor compliance. Intraoperatively measured electrically evoked stapedius reflexes (eSR) can be used as a marker for the patient’s discomfort level. The aim of this study was to develop and evaluate an automated detection method for eSR and to compare it to the detection rate of the surgeon and independent observers.

Methods

Cochlear implantation using a fully digital surgical microscope was performed. Movements of the stapedius tendon were recorded and analyzed by means of computer vision technique. Differences in eSR elicited by stimulating electrodes at different cochlear locations (basal, middle and apical) were analyzed. The eSR detection rate of the image processing algorithm was compared to the surgeon’s detection rate and to those of two less experienced observers.

Results

A total of 387 electrically impulses were applied. The stimulation of middle turn electrodes showed significantly higher detection rates (50.4%) compared to the basal (40.0%; p = 0.001) and apical (43.6%; p = 0.03) turn. The software identified significantly more of the applied stimuli (58.4%) compared to the surgeon (46.3%; p = 0.0007), the intermediate observer (37.7%; p < 0.0001) and the unexperienced observer (41.3%; p < 0.0001).

Conclusion

The feasibility of an automated intraoperative software-based detection of eSR is demonstrated. By improving the eSR detection methods and their clinical applicability, their utility in objective cochlear implant fitting may be substantially increased.

Multi-electrode sequential versus single electrode stimulation to elicit the stapedial reflex during cochlear implantation: Correlation with maximum comfort level

OBJECTIVES

To assess whether electrical stimulation sequentially delivered through 4 electrodes located in different cochlear areas may elicit the stapedial reflex at lower levels compared to single electrode stimulation and to correlate the sequentially obtained values with the maximum comfort level (C-level).

PATIENTS AND METHODS

A retrospective study was performed on 35 post-verbal adult patients (age 19-80 years) consecutively implanted in 2 cochlear implant centers, evaluating the level of stimulation (pulse width) necessary to electrically evoke the stapedial reflex with two different stimulation modalities: single electrode versus sequential 4 electrode stimulation. Threshold values were compared with C-level obtained at activation.

RESULTS

The average differences of pulse width and C-level were significantly smaller (P<0.0001) when the stapedial reflex was obtained with the sequential stimulation modality and reached statistical significance for every single electrode (P<0.0001).

CONCLUSIONS

Stapedial reflex thresholds obtained with sequential stimulation through 4 different electrodes significantly correlate to the C-level obtained at the first setting and may be helpful in defining the upper limit of the dynamic field during initial CI mapping.

Contralateral suppression of human hearing sensitivity in single-sided deaf cochlear implant users

Cochlear implants (CIs) are being implanted in people with unilateral hearing loss because they can improve speech intelligibility and sound source localization. Though designed to restore the afferent auditory stimulation, the CI possibly restores some efferent effects. The present study aimed at investigating this possibility. Five single-sided deaf CI users with less than 30 dB hearing loss up to 4 kHz in their acoustic ear participated in the study. Absolute thresholds for their acoustic ears were measured for pure tones of 500 and 4000 Hz with durations of 10 and 200 ms in the presence and in the absence of contralateral broadband electrical stimulation (CBES) delivered with the CI. The electrical stimulus consisted of pulse trains (symmetric biphasic pulses with phase duration 36 μs) on all 16 electrodes sequentially stimulated at a rate of 843 Hz. Its intensity was set to sound as loud as broadband noise at 50 or 60 dB SPL in the acoustic ear. Thresholds were measured using a three-interval, three-alternative, forced-choice procedure with a two-down, one-up adaptive rule to estimate the level for 71% correct in the psychometric function. Thresholds measured without the CBES were lower for the longer than for the shorter tones, and the difference was larger at 500 than at 4000 Hz. CBES equivalent to 50 or 60 dB SPL caused significant threshold elevation only for short (10 ms) and low frequency (500 Hz) acoustic tones of 1.2 and 2.2 dB. These increases appear smaller than previously reported for normal hearing listeners in related experiments. These results support the notion that for single-sided deaf CI users, the CI modulates hearing in the acoustic ear. The possible mechanisms that may be contributing this effect are discussed.

Electrically-evoked auditory steady-state responses as neural correlates of loudness growth in cochlear implant users

Loudness growth functions characterize how the loudness percept changes with current level between the threshold and most comfortable loudness level in cochlear implant users. Even though loudness growth functions are highly listener-dependent, currently default settings are used in clinical devices. This study investigated whether electrically-evoked auditory steady-state response amplitude growth functions correspond to behaviorally measured loudness growth functions. Seven cochlear implant listeners participated in two behavioral loudness growth tasks and an EEG recording session. The 40-Hz sinusoidally amplitude-modulated pulse trains were presented to CI channels stimulating at a more apical and basal region of the cochlea, and were presented at different current levels encompassing the listeners' dynamic ranges. Behaviorally, loudness growth was measured using an Absolute Magnitude Estimation and a Graphic Rating Scale with loudness categories. A good correspondence was found between the response amplitude functions and the behavioral loudness growth functions. The results are encouraging for future advances in individual, more automatic, and objective fitting of cochlear implants.

The importance of electrically evoked stapedial reflex in cochlear implant

Introdução

A determinação da área dinâmica do implante coclear é um dos procedimentos mais importantes em sua programação. O uso de medidas objetivas, em especial a do limiar do reflexo estapédico evocado eletricamente, pode contribuir para a definição deste campo, principalmente em crianças ou em indivíduos com múltiplos comprometimentos, pois fornecem valores específicos que servem como base no início da programação do implante coclear.

Objetivo

Verificar por meio de uma revisão a utilização do limiar do reflexo estapédico evocado ele- tricamente durante o processo de ativação e de mapeamento do implante coclear. Métodos: Levantamento bibliográfico nas plataformas Pubmed e Bireme e nas bases de dados MedLine, LILACS e SciELO, com buscas padronizadas até setembro de 2012, utilizando-se palavras-chave. Para a seleção e avaliação dos estudos científicos levantados, foram estabelecidos critérios, contemplando os seguintes aspectos: autor, ano/local, grau de recomendação/nível de evidência científica, objetivo, amostra, faixa etária, média de idade em anos, testes avaliativos, resultados e conclusão.

Resultados

Dos 7.304 artigos encontrados, 7.080 foram excluídos pelo título, 152 pelo resumo, 17 pela leitura do artigo, 43 eram repetidos e 12 foram selecionados para o estudo. Conclusão: O reflexo estapédico evocado eletricamente é capaz de auxiliar na programação do implante coclear, principalmente em pacientes que apresentam respostas inconsistentes.

© 2014 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Publicado por Elsevier Editora Ltda. Todos os direitos reservados.