Effect of low frequency on speech performance with bimodal hearing in bilateral severe hearing loss

An overview of factors affecting bimodal and electric-acoustic stimulation (EAS) speech understanding outcomes

Improvements in device technology, surgical technique, and patient outcomes have resulted in a broadening of cochlear implantation criteria to consider those with increasing levels of useful low-to-mid frequency residual acoustic hearing. Residual acoustic hearing allows for the addition of a hearing aid (HA) to complement the cochlear implant (CI) and has demonstrated enhanced listening outcomes. However, wide inter-subject outcome variability exists and thus identification of contributing factors would be of clinical interest and may aid with pre-operative patient counselling. The optimal fitting procedure and frequency assignments for the two hearing devices used in combination to enhance listening outcomes also remains unclear. The understanding of how acoustic and electric speech information is fundamentally combined and utilised by the listener may allow for the optimisation of device fittings and frequency allocations to provide best bimodal and electric-acoustic stimulation (EAS) patient outcomes. This article will provide an overview of contributing factors to bimodal and EAS listening outcomes, explore areas of contention, and discuss common study limitations.

Study protocol for a randomised controlled trial evaluating the benefits from bimodal solution with cochlear implant and hearing aid versus bilateral hearing aids in patients with asymmetric speech identification scores

INTRODUCTION

Cochlear implant (CI) and hearing aid (HA) in a bimodal solution (CI+HA) is compared with bilateral HAs (HA+HA) to test if the bimodal solution results in better speech intelligibility and self-reported quality of life.

METHODS AND ANALYSIS

This randomised controlled trial is conducted in Odense University Hospital, Denmark. Sixty adult bilateral HA users referred for CI surgery are enrolled if eligible and undergo: audiometry, speech perception in noise (HINT: Hearing in Noise Test), Speech Identification Scores and video head impulse test. All participants will receive new replacement HAs. After 1 month they will be randomly assigned (1:1) to the intervention group (CI+HA) or to the delayed intervention control group (HA+HA). The intervention group (CI+HA) will receive a CI on the ear with a poorer speech recognition score and continue using the HA on the other ear. The control group (HA+HA) will receive a CI after a total of 4 months of bilateral HA use.The primary outcome measures are speech intelligibility measured objectively with HINT (sentences in noise) and DANTALE I (words) and subjectively with the Speech, Spatial and Qualities of Hearing scale questionnaire. Secondary outcomes are patient reported Health-Related Quality of Life scores assessed with the Nijmegen Cochlear Implant Questionnaire, the Tinnitus Handicap Inventory and Dizziness Handicap Inventory. Third outcome is listening effort assessed with pupil dilation during HINT.In conclusion, the purpose is to improve the clinical decision-making for CI candidacy and optimise bimodal solutions.

ETHICS AND DISSEMINATION

This study protocol was approved by the Ethics Committee Southern Denmark project ID S-20200074G. All participants are required to sign an informed consent form.This study will be published on completion in peer-reviewed publications and scientific conferences.

TRIAL REGISTRATION NUMBER

NCT04919928.

Efficacy of hearing aid treatment on sound perception and residual hearing preservation in patients with tinnitus and coexisting hearing loss: study protocol for a randomized controlled trial

BACKGROUND

Chronic subjective tinnitus poses significant challenges in clinical practice, and it is usually associated with hearing impairment, particularly with high-frequency sensorineural hearing loss (SNHL). Patients suffering from tinnitus with SNHL experience one of the most severe sensory disabilities, and this has devastating effects on their quality of life. Nowadays, mild to moderate SNHL can be managed with a properly fitted hearing aid (HA) that provides sound amplification, and several studies suggest that HAs may also benefit those with tinnitus. However, inadequate attention has been paid by medical personnel to the impact of HA use in residual hearing protection for patients with tinnitus and coexisting SNHL, and existing evidence is still at a preliminary stage. This study aims to identify and evaluate the efficacy of the use of HAs in both sound perception and residual hearing preservation among patients with tinnitus and coexisting SNHL.

METHODS AND DESIGN

The present study is a prospective, single-center, outcome assessor and data analyst-blinded, randomized, controlled trial. Eligible participants will be recruited and randomly allocated into the HA intervention group and the waiting list control group at a ratio of 1:1. The primary outcome is to evaluate the severity of tinnitus using the Tinnitus Handicap Inventory as a continuous variable at 6 months from randomization. Secondary outcome measures include changes in hearing status and mental states. The trial will last 6 months, with follow-up visits at 3 months and 6 months.

DISCUSSION

This will be the first randomized, controlled trial to identify and evaluate HAs' efficacy on residual hearing preservation among tinnitus patients with coexisting high-frequency SNHL in China. We are aiming for novelty and generalizability, and strengths of this study are that it will examine the effectiveness of HA in patients with tinnitus and hearing impairment and will further explore the residual hearing protection provided by HA treatment in the tinnitus group.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05343026. Registered on April 25, 2022.

The Temporal Fine Structure of Background Noise Determines the Benefit of Bimodal Hearing for Recognizing Speech

Cochlear implant (CI) users have more difficulty understanding speech in temporally modulated noise than in steady-state (SS) noise. This is thought to be caused by the limited low-frequency information that CIs provide, as well as by the envelope coding in CIs that discards the temporal fine structure (TFS). Contralateral amplification with a hearing aid, referred to as bimodal hearing, can potentially provide CI users with TFS cues to complement the envelope cues provided by the CI signal. In this study, we investigated whether the use of a CI alone provides access to only envelope cues and whether acoustic amplification can provide additional access to TFS cues. To this end, we evaluated speech recognition in bimodal listeners, using SS noise and two amplitude-modulated noise types, namely babble noise and amplitude-modulated steady-state (AMSS) noise. We hypothesized that speech recognition in noise depends on the envelope of the noise, but not on its TFS when listening with a CI. Secondly, we hypothesized that the amount of benefit gained by the addition of a contralateral hearing aid depends on both the envelope and TFS of the noise. The two amplitude-modulated noise types decreased speech recognition more effectively than SS noise. Against expectations, however, we found that babble noise decreased speech recognition more effectively than AMSS noise in the CI-only condition. Therefore, we rejected our hypothesis that TFS is not available to CI users. In line with expectations, we found that the bimodal benefit was highest in babble noise. However, there was no significant difference between the bimodal benefit obtained in SS and AMSS noise. Our results suggest that a CI alone can provide TFS cues and that bimodal benefits in noise depend on TFS, but not on the envelope of the noise.

A Predictive Model for Cochlear Implant Outcome in Children with Cochlear Nerve Deficiency

The outcome of cochlear implantation (CI) in patients with cochlear nerve deficiency (CND) is variable, resulting in a wide range of speech perception performance, from degrees of environmental sound perception to conversation without lip-reading. Twenty-five cochlear implantees with CND were enrolled retrospectively to determine the factors correlated with CI outcome in patients with CND and to develop a predictive model for CI outcome. CI outcome was evaluated using the Categories of Auditory Performance (CAP) score at 2 years after CI. Patients with negative auditory brainstem response (ABR) showed a significantly lower CAP score than those with positive ABR (2.5 ± 1.7, 4.8 ± 0.7; p = 0.001). The area ratio of vestibulocochlear nerve (VCN) to facial nerve (FN) at the cerebellopontine angle on magnetic resonance images was positively correlated with CI outcome (p < 0.001). With multiple regression analysis, a predictive equation accounting for 66% of variance of CAP score at 2 years after CI was \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\bf{deduced}}:{\bf{CAP}}\,{\bf{score}}{\boldsymbol{=}}{\bf{0.7}}{\boldsymbol{+}}{\bf{1.9}}{\boldsymbol{\ast }}{\boldsymbol{(}}{\bf{ABR}}{\boldsymbol{)}}{\boldsymbol{+}}{\bf{1.2}}{\boldsymbol{\ast }}(\frac{{\boldsymbol{V}}{\boldsymbol{C}}{\boldsymbol{N}}}{{\boldsymbol{F}}{\boldsymbol{N}}})$$\end{document}deduced:CAPscore=0.7+1.9∗(ABR)+1.2∗(VCNFN). We found that preoperative ABR and area ratio of VCN to FN at the cerebellopontine angle could predict CI outcome in patients with CND. Preoperative counselling based on our predictive model might be helpful to determine treatment modality for auditory rehabilitation and which ear to implant.

Performance variability on perceptual discrimination tasks in profoundly deaf adults with cochlear implants

OBJECTIVES

The purpose of this study was to evaluate performance on two challenging listening tasks, talker and regional accent discrimination, and to assess variables that could have affected the outcomes.

STUDY DESIGN

A prospective study using 35 adults with one cochlear implant (CI) or a CI and a contralateral hearing aid (bimodal hearing) was conducted. Adults completed talker and regional accent discrimination tasks.

METHODS

Two-alternative forced-choice tasks were used to assess talker and accent discrimination in a group of adults who ranged in age from 30 years old to 81 years old.

RESULTS

A large amount of performance variability was observed across listeners for both discrimination tasks. Three listeners successfully discriminated between talkers for both listening tasks, 14 participants successfully completed one discrimination task and 18 participants were not able to discriminate between talkers for either listening task. Some adults who used bimodal hearing benefitted from the addition of acoustic cues provided through a HA but for others the HA did not help with discrimination abilities. Acoustic speech feature analysis of the test signals indicated that both the talker speaking rate and the fundamental frequency (F0) helped with talker discrimination. For accent discrimination, findings suggested that access to more salient spectral cues was important for better discrimination performance.

CONCLUSIONS

The ability to perform challenging discrimination tasks successfully likely involves a number of complex interactions between auditory and non-auditory pre- and post-implant factors. To understand why some adults with CIs perform similarly to adults with normal hearing and others experience difficulty discriminating between talkers, further research will be required with larger populations of adults who use unilateral CIs, bilateral CIs and bimodal hearing.