Rehabilitation for unilateral deafness - Narrative review comparing a novel bone conduction solution with existing options.

Patients with single sided deafness (SSD) struggle with sound localization and speech in noise. Existing treatment options include contralateral routing of signal (CROS) systems, percutaneous bone conduction hearing devices (BCHDs), passive transcutaneous BCHDs, active BCHDs, and cochlear implants. Implanted devices provide benefits in speech in noise compared to CROS devices. Percutaneous BCHDs transmit sound efficiently but have aesthetic drawbacks and skin complications. Scalp attenuation impacts passive transcutaneous BCHD performance. Active BCHDs overcome these issues and provide benefits for speech in noise. Cochlear implantation is the only existing option that restores binaural input but introduces electrical rather than acoustic stimuli to the deaf ear. Active BCHDs have been designed to maintain efficient sound transmission and avoid chronic skin irritation and cosmetic concerns that may occur with percutaneous BCHDs. Cochlear implantation may be a superior option for recently deafened SSD patients, though this requires further study. The duration of deafness, patient age and comorbidities, and a shared decision-making model among patients, surgeons, and audiologists should be considered in device selection. The aim of this manuscript is to review available devices, discuss surgical considerations for implantable devices, review available published results for speech in noise and sound quality with each device, and provide an overview to guide shared decision making for patients and providers. This review consolidates available literature and reviews experience with a newer active transcutaneous active BCHD available for use in the SSD population.

Prediction of hearing outcomes by auditory steady-state response in patients with sudden sensorineural hearing loss.

BACKGROUND: There has been no report on the predictive value of auditory steady-state response (ASSR) in the hearing prognosis of sudden sensorineural hearing loss (SSNHL). AIMS/OBJECTIVES: To investigate whether ASSR can be a prognostic indicator of hearing outcome in patients with SSNHL after systemic steroid treatment. MATERIAL AND METHODS: Fifty-three patients with unilateral mild to severe SSNHL (≤90 dB HL at 0.5k, 1k, 2k, and 4 kHz, 4FA) were included. All patients received systemic high dose steroid therapy within one month after onset. The difference between the threshold levels measured by ASSR and PTA on the same day [ASSR - PTA] was calculated. The hearing recovery (HR) was defined as a < 30 dB HL of final degree of hearing loss and a > 15 dB HL of hearing gain. RESULTS: The HR (+) group showed significantly worse ASSR predicted threshold than pure-tone threshold in univariate (t(51) = 2.412, p = .020) and multivariate analysis (OR 0.910, p = .012). The [ASSR - PTA] threshold showed significantly moderate correlation with hearing gain (r = -0.303, p = .028). CONCLUSIONS: Worse ASSR predicted threshold than pure-tone threshold predicted poor hearing outcome after systemic steroid treatment in mild to severe unilateral SSNHL.

Association Between Hearing Loss and Postural Instability in Older Korean Adults.

Importance: Hearing loss is one of the most frequently occurring sensory disabilities worldwide. The association between hearing loss and postural instability in an older population remains to be studied. Objective: To determine whether the odds of postural instability increase with the degree of hearing loss and to suggest criteria for hearing rehabilitation for postural instability. Design, Setting, and Participants: This cross-sectional population-based study of 3864 participants 40 years and older with hearing loss used data from 2010 through 2012 in the fifth edition of the Korea National Health and Nutrition Examination Survey, a nationwide survey of South Korea. Pure tone audiometry was performed on both the left and right sides and each hearing grade of each side was classified into 1 of 3 subcategories: normal hearing, mild hearing loss, or moderate hearing loss (moderate hearing loss or worse). Postural instability was defined as the failure to remain standing on a foam pad surface with feet 10 cm apart with arms folded and hands cupping the elbows and eyes closed. A binomial logistic regression model was used to assess the association between hearing loss and postural instability. Data were analyzed from August 18, 2019, to September 2, 2019. Exposures: Age-related hearing loss defined as a threshold of 26 dB or more. Main Outcomes and Measures: The degree of hearing loss and postural instability. Results: Of the 3864 participants included in the study, the mean (SD) age was 57.8 (11.3) years and 2135 (55.2%) were women. Female sex was associated with higher odds of postural instability compared with male sex (odds ratio [OR], 1.65; 95% CI, 1.12-2.42, adjusted for age and hearing status), and the odds of postural instability increased with every 1 year increase in age (OR, 1.13; 95% CI, 1.10-1.16, adjusted for sex and hearing status). Unilateral or bilateral mild hearing loss was not associated with an increase in the odds of postural instability, but moderate hearing loss present on at least 1 side was associated with an increase in the odds of postural instability: unilateral moderate hearing loss group (OR, 2.71; 95% CI, 1.12-6.10, adjusted for age and sex), one mild and the other moderate hearing loss group (OR, 2.18; 95% CI, 1.16-4.09, adjusted for age and sex), and bilateral moderate hearing loss group (OR, 2.34; 95% CI, 1.27-4.33, adjusted for age and sex). Conclusions and Relevance: Aging, female sex, and having hearing loss were associated with postural instability in this analysis. Moderate or worse hearing loss present on at least 1 side was associated with increased odds of postural instability. Future research in this area is warranted to identify more precise interrelationships and preventive measures.

Low-Frequency Hearing Preservation With Long Electrode Arrays: Inclusion of Unaided Hearing Threshold Assessment in the Postoperative Test Battery.

Purpose The goal of this work was to evaluate the low-frequency hearing preservation of long electrode array cochlear implant (CI) recipients. Method Twenty-five participants presented with an unaided hearing threshold of ≤ 80 dB HL at 125 Hz pre-operatively in the ear to be implanted. Participants were implanted with a long (31.5-mm) electrode array. The unaided hearing threshold at 125 Hz was compared between the preoperative and postoperative intervals (i.e., initial CI activation, and 1, 3, 6, 9, and 12 months after activation). Results Eight participants maintained an unaided hearing threshold of ≤ 80 dB HL at 125 Hz postoperatively. The majority (n = 5) demonstrated aidable low-frequency hearing at initial activation, whereas 3 other participants experienced an improvement in unaided low-frequency hearing thresholds at subsequent intervals. Conclusions CI recipients can retain residual hearing sensitivity with fully inserted long electrode arrays, and low-frequency hearing thresholds may improve during the postoperative period. Therefore, unaided hearing thresholds obtained within the initial weeks after surgery may not reflect later hearing sensitivity. Routine measurement of postoperative unaided hearing thresholds-even for patients who did not demonstrate aidable hearing thresholds initially after cochlear implantation-will identify CI recipients who may benefit from electric-acoustic stimulation. Supplemental Material https://doi.org/10.23641/asha.11356637.

An fMRI-study on single-sided deafness: Spectral-temporal properties and side of stimulation modulates hemispheric dominance.

OBJECTIVE: Our main aim was to investigate the blood oxygenation level dependent (BOLD) response to monaural and binaural speech- and non-speech stimuli as measured with fMRI in subjects with single-sided deafness and in normal hearing controls. We hypothesised that the response to monaural stimulation in both normal hearing subjects and persons with single-sided deafness would vary with the complexity and nature of the stimuli and the side of stimulation. DESIGN: Patients with left- and right single-sided deafness and controls with normal hearing receiving either binaural or monaural stimuli were tested using speech and non-speech auditory stimuli in an event-related fMRI experiment. STUDY SAMPLE: Twenty-two patients with single-sided deafness after treatment for vestibular schwannoma and 50 normal hearing controls. RESULTS: Normal hearing persons receiving right side monaural stimuli activate bilateral temporal regions. Activation following left side monaural stimulation is more right lateralized. Persons with single-sided deafness respond similarly to controls to monaural stimulation. Persons with right side single-sided deafness show activation of frontal cortical regions not seen in persons with left side single-sided deafness following speech stimuli. This is possibly related to increased effort and more frequently reported problems with communication. Right side single-sided deafness is related to increased activation of areas usually related to processing of degraded input, including the thalamus. CONCLUSION: Hemispheric dominance following monaural auditory stimulation is modulated by the spectral-temporal properties of the stimuli and by which ear is stimulated. Differences between patients with right- and left side deafness suggests that right side deafness is related to increased activation of areas involved in processing of degraded input.

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.

Improved interaural timing of acoustic nerve stimulation affects sound localization in single-sided deaf cochlear implant users.

The main impairment associated with single-sided deafness (SSD) is the loss of binaural hearing. Currently, the most effective treatment to compensate for this deficit is to supply patients suffering from SSD with a cochlear implant (CI) in the deaf ear. With this approach binaural hearing abilities can be restored to a certain extent, which is expressed in an improvement in such patients with regard to sound source localization and speech comprehension in noise after receipt of a CI. However, binaural performance of these listeners does not reach the level of normal-hearing listeners. One of the reasons for this might be that the electrical stimulation via CI and the physiological stimulation via the intact ear are not synchronized: the CI transmits the information to the auditory nerve with different timing than does the intact inner ear. As a result, there is a timing mismatch of the information transfer between the left and the right side, which may account for the limited binaural performance. The effective mismatch in timing depends on the CI system because of different stimulation strategies implemented in devices from different manufacturers. For the particular CI device used in this study (MED-EL Mi1000/Mi1200) electrical stimulation led to faster activation of the auditory nerve than natural for a wide frequency range. In particular, electrical stimulation was about 1 to up to 2 ms ahead of time for frequencies above 1.5 kHz. Hence, it was hypothesized that information transfer between the left and the right ear can be tuned by delaying the CI signal. The goal of the present study was to investigate whether such a delay in the CI signal affects binaural performance of CI users with SSD. For this purpose, sound source localization and speech perception in noise were tested in a sample of 12 CI users with SSD (mean age 51 ±â€¯12 years). The tests were performed for four different delay times of the CI signal applied spontaneously (0.5, 1, 2 and 4 ms) and for the base line condition "no delay" in the CI signal (i.e. everyday use). It was found that delaying the signal had a significant impact on sound source localization. Speech perception in noise was affected, but less pronounced than was sound localization. Regarding sound source localization, a signal delay of 1 ms applied to this particular CI device produced the best performance in our patients. It is concluded that improving the synchronisation between the CI-transferred signal and the naturally transferred signal could increase binaural hearing performance in CI users with SSD.

Effect of Tinnitus and Duration of Deafness on Sound Localization and Speech Recognition in Noise in Patients With Single-Sided Deafness.

Patients with single-sided deafness (SSD) often experience poor sound localization, reduced speech understanding in noise, reduced quality of life, and tinnitus. The present study aims to evaluate effects of tinnitus and duration of deafness on sound localization and speech recognition in noise by SSD subjects. Sound localization and speech recognition in noise were measured in 26 SSD and 10 normal-hearing (NH) subjects. Speech was always presented directly in front of the listener. Noise was presented to the deaf ear, in front of the listener, or to the better hearing ear. Tinnitus severity was measured using visual analog scale and Tinnitus Handicap Inventory. Relative to NH subjects, SSD subjects had significant deficits in sound localization and speech recognition in all listening conditions ( p < .001). For SSD subjects, speech recognition in noise was correlated with mean hearing thresholds in the better hearing ear ( p < .001) but not in the deaf ear. SSD subjects with tinnitus performed poorer in sound localization and speech recognition in noise than those without tinnitus. Shorter duration of deafness was associated with greater tinnitus and sound localization difficulty. Tinnitus visual analog scale and Tinnitus Handicap Inventory were highly correlated; the degree of tinnitus was negatively correlated with sound localization and speech recognition in noise. Those experiencing noticeable tinnitus may benefit more from cochlear implantation than those without; subjective tinnitus reduction may be correlated with improved sound localization and speech recognition in noise. Subjects with longer duration of deafness demonstrated better sound localization, suggesting long-term compensation for loss of binaural cues.

The effect of simulated unilateral hearing loss on horizontal sound localization accuracy and recognition of speech in spatially separate competing speech.

Unilateral hearing loss (UHL) occurs in 25% of cases of congenital sensorineural hearing loss. Due to the unilaterally reduced audibility associated with UHL, everyday demanding listening situations may be disrupted despite normal hearing in one ear. The aim of this study was to quantify acute changes in recognition of speech in spatially separate competing speech and sound localization accuracy, and relate those changes to two levels of temporary induced UHL (UHL30 and UHL43; suffixes denote the average hearing threshold across 0.5, 1, 2, and 4 kHz) for 8 normal-hearing adults. A within-subject repeated-measures design was used (normal binaural conditions, UHL30 and UHL43). The main outcome measures were the threshold for 40% correct speech recognition and the overall variance in sound localization accuracy quantified by an Error Index (0 = perfect performance, 1.0 = random performance). Distinct and statistically significant deterioration in speech recognition (2.0 dB increase in threshold, p < 0.01) and sound localization (Error Index increase of 0.16, p < 0.001) occurred in the UHL30 condition. Speech recognition did not significantly deteriorate further in the UHL43 condition (1.0 dB increase in speech recognition threshold, p > 0.05), while sound localization was additionally impaired (Error Index increase of 0.33, p < 0.01) with an associated large increase in individual variability. Qualitative analyses on a subject-by-subject basis showed that high-frequency audibility was important for speech recognition, while low-frequency audibility was important for horizontal sound localization accuracy. While the data might not be entirely applicable to individuals with long-standing UHL, the results suggest a need for intervention for mild-to-moderate UHL.

Brain activity in patients with unilateral sensorineural hearing loss during auditory perception in noisy environments.

Patients with unilateral sensorineural hearing loss (UHL) often complain of hearing difficulties in noisy environments. To clarify this, we compared brain activation in patients with UHL with that of healthy participants during speech perception in a noisy environment, using functional magnetic resonance imaging (fMRI). A pure tone of 1 kHz, or 14 monosyllabic speech sounds at 65‒70 dB accompanied by MRI scan noise at 75 dB, were presented to both ears for 1 second each and participants were instructed to press a button when they could hear the pure tone or speech sound. Based on the activation areas of healthy participants, the primary auditory cortex, the anterior auditory association areas, and the posterior auditory association areas were set as regions of interest (ROI). In each of these regions, we compared brain activity between healthy participants and patients with UHL. The results revealed that patients with right-side UHL showed different brain activity in the right posterior auditory area during perception of pure tones versus monosyllables. Clinically, left-side and right-side UHL are not presently differentiated and are similarly diagnosed and treated; however, the results of this study suggest that a lateralityspecific treatment should be chosen.

[Advances in effect of unilateral auditory deprivation on sound localization].

In patients with single-sided deafness (SSD), the interaural time difference and the interaural level difference signals are insufficient or missing, which result in the lack of sound localization ability and the decrease of speech comprehension in the noise environments. SSD can also cause the morphological and functional changes of the central auditory system, resulting in auditory deprivation. In early stage of the development, the auditory center is more susceptible to ambient environment and auditory inputs. It is a critical period of auditory function and morphological refinement. It is also sensitive period of central adaptability after auditory deprivation. SSD in the sensitive period of development can cause significant laterality activities of bilateral sound localization pathway. Unilateral auditory deprivation can distort tonotopic maps, disrupt the binaural integration, reorganize the neural network and change the synaptic transmission in the primary auditory cortex or sub cortex. In order to compensate for the deficiency of the interaural time difference and interaural level difference cues, the auditory pathway is used to improve the ability of sound source localization by using the spectral-shape cues remaining unchanged. In order to improve the effectiveness of the functional areas of the cortex, auditory center is also reorganized by cross-modal. However, central compensation after SSD is a double-edged sword. If SSD onset in the sensitive period, the laterality of auditory pathway will be continued and difficult to reverse by even long term bilateral hearing in the post-sensitive period. Therefore, in order to improve the understanding of the characteristics of unilateral auditory deprivation, this paper reviewed the evidence for adaptive changes in spatial hearing following a developmental hearing loss in one ear.

Speech perception in noise in unilateral hearing loss / Percepção da fala no ruído em perda auditiva unilateral

ABSTRACT INTRODUCTION: Unilateral hearing loss is characterized by a decrease of hearing in one ear only. In the presence of ambient noise, individuals with unilateral hearing loss are faced with greater difficulties understanding speech than normal listeners. OBJECTIVE: To evaluate the speech perception of individuals with unilateral hearing loss in speech perception with and without competitive noise, before and after the hearing aid fitting process. METHODS: The study included 30 adults of both genders diagnosed with moderate or severe sensorineural unilateral hearing loss using the Hearing In Noise Test - Hearing In Noise Test-Brazil, in the following scenarios: silence, frontal noise, noise to the right, and noise to the left, before and after the hearing aid fitting process. RESULTS: The study participants had a mean age of 41.9 years and most of them presented right unilateral hearing loss. In all cases evaluated with Hearing In Noise Test, a better performance in speech perception was observed with the use of hearing aids. CONCLUSION: Using the Hearing In Noise Test-Brazil test evaluation, individuals with unilateral hearing loss demonstrated better performance in speech perception when using hearing aids, both in silence and in situations with a competing noise, with use of hearing aids.

Resumo Introdução: A perda auditiva unilateral (PAUn) é caracterizada pela diminuição da audição em apenas uma orelha. Em presença de ruído ambiental, indivíduos com PAUn encontram maiores dificuldades que os ouvintes normais para compreender a fala. Objetivo: Avaliar o desempenho de indivíduos com perda auditiva unilateral, na percepção da fala sem e com ruído competidor, antes a após adaptação do AASI. Método: Estudo com 30 adultos, e de ambos os sexos, com diagnóstico de perda auditiva unilateral sensorioneural, de graus moderado e severo, utilizando o Hearing In Noise Test - HINT - Brasil, nas seguintes situações: silêncio, ruído à frente, ruído a direita e ruído a esquerda. Antes e após adaptação do AASI. Resultados: Os participantes da pesquisa apresentavam média de idade de 41,9 anos e PAUn predominante à direita. Em todas as situações propostas pelo HINT foi constatado melhor desempenho na percepção da fala com o uso do AASI. Conclusão: No teste HINT - Brasil, indivíduos com PAUn demonstraram melhor desempenho napercepção da fala, em tanto no silêncio quanto nas situações com ruído competidor, com usodo AASI.

The effect of symmetrical and asymmetrical hearing impairment on music quality perception.

The purpose of this study was to investigate the effect of symmetrical, asymmetrical and unilateral hearing impairment on music quality perception. Six validated music pieces in the categories of classical music, folk music and pop music were used to assess music quality in terms of its 'pleasantness', 'naturalness', 'fullness', 'roughness' and 'sharpness'. 58 participants with sensorineural hearing loss [20 with unilateral hearing loss (UHL), 20 with bilateral symmetrical hearing loss (BSHL) and 18 with bilateral asymmetrical hearing loss (BAHL)] and 29 normal hearing (NH) subjects participated in the present study. Hearing impaired (HI) participants had greater difficulty in overall music quality perception than NH participants. Participants with BSHL rated music pleasantness and naturalness to be higher than participants with BAHL. Moreover, the hearing thresholds of the better ears from BSHL and BAHL participants as well as the hearing thresholds of the worse ears from BSHL participants were negatively correlated to the pleasantness and naturalness perception. HI participants rated the familiar music pieces higher than unfamiliar music pieces in the three music categories. Music quality perception in participants with hearing impairment appeared to be affected by symmetry of hearing loss, degree of hearing loss and music familiarity when they were assessed using the music quality rating test (MQRT). This indicates that binaural symmetrical hearing is important to achieve a high level of music quality perception in HI listeners. This emphasizes the importance of provision of bilateral hearing assistive devices for people with asymmetrical hearing impairment.

Induction of single-sided deafness in the newborn rat and its consequence for cochlear nucleus volume development.

Aim of this study was to induce a single-sided deafness (SSD) in rats before hearing onset. Rats were operated at postnatal day 10 by approaching the tympanic cavity along a retroauricular path without manipulating ossicles or tympanic membrane. The ototoxic aminoglycoside neomycin was injected intracochlearly through the round window membrane on one side. When the animals have reached young adult stages, their hearing threshold was determined by their auditory brainstem response (ABR). Monaural deafening was considered successful when the hearing threshold was at least 95 dB above the threshold of the normal hearing ear. Growing up with one non-functional ear, rats developed a striking anatomical asymmetry of their cochlear nuclei (CN). The CN from age-matched normal hearing brains and from both sides of single-sided deaf brains were cut into series of frontal sections and their volumes calculated. No difference was detected between the volume of the normal hearing CN and the contralateral CN in SSD rats. By contrast, growth retardation was found for the ventral CN on the deaf side to result in a volume of only 57% compared to the normal hearing side. Marginal growth retardation was also observed for the dorsal CN on the deaf side. Thus, loss of sensory activation leads mainly, but not exclusively, to a reduction of tissue volume in the ventral CN of the deaf side, leaving the contralateral side apparently unaffected.

Functional-structural reorganisation of the neuronal network for auditory perception in subjects with unilateral hearing loss: Review of neuroimaging studies.

OBJECTIVE: This paper aims to provide a review of studies using neuroimaging to measure functional-structural reorganisation of the neuronal network for auditory perception after unilateral hearing loss. DESIGN: A literature search was performed in PubMed. Search criterions were peer reviewed original research papers in English completed by the 11th of March 2015. STUDY SAMPLE: Twelve studies were found to use neuroimaging in subjects with unilateral hearing loss. An additional five papers not identified by the literature search were provided by a reviewer. Thus, a total of 17 studies were included in the review. RESULTS: Four different neuroimaging methods were used in these studies: Functional magnetic resonance imaging (fMRI) (n = 11), diffusion tensor imaging (DTI) (n = 4), T1/T2 volumetric images (n = 2), magnetic resonance spectroscopy (MRS) (n = 1). One study utilized two imaging methods (fMRI and T1 volumetric images). CONCLUSION: Neuroimaging techniques could provide valuable information regarding the effects of unilateral hearing loss on both auditory and non-auditory performance. fMRI-studies showing a bilateral BOLD-response in patients with unilateral hearing loss have not yet been followed by DTI studies confirming their microstructural correlates. In addition, the review shows that an auditory modality-specific deficit could affect multi-modal brain regions and their connections.

Speech perception in noise in unilateral hearing loss.

INTRODUCTION: Unilateral hearing loss is characterized by a decrease of hearing in one ear only. In the presence of ambient noise, individuals with unilateral hearing loss are faced with greater difficulties understanding speech than normal listeners. OBJECTIVE: To evaluate the speech perception of individuals with unilateral hearing loss in speech perception with and without competitive noise, before and after the hearing aid fitting process. METHODS: The study included 30 adults of both genders diagnosed with moderate or severe sensorineural unilateral hearing loss using the Hearing In Noise Test - Hearing In Noise Test-Brazil, in the following scenarios: silence, frontal noise, noise to the right, and noise to the left, before and after the hearing aid fitting process. RESULTS: The study participants had a mean age of 41.9 years and most of them presented right unilateral hearing loss. In all cases evaluated with Hearing In Noise Test, a better performance in speech perception was observed with the use of hearing aids. CONCLUSION: Using the Hearing In Noise Test-Brazil test evaluation, individuals with unilateral hearing loss demonstrated better performance in speech perception when using hearing aids, both in silence and in situations with a competing noise, with use of hearing aids.

Towards a Unified Testing Framework for Single-Sided Deafness Studies: A Consensus Paper.

BACKGROUND: While hearing aids for a contralateral routing of signals (CROS-HA) and bone conduction devices have been the traditional treatment for single-sided deafness (SSD) and asymmetric hearing loss (AHL), in recent years, cochlear implants (CIs) have increasingly become a viable treatment choice, particularly in countries where regulatory approval and reimbursement schemes are in place. Part of the reason for this shift is that the CI is the only device capable of restoring bilateral input to the auditory system and hence of possibly reinstating binaural hearing. Although several studies have independently shown that the CI is a safe and effective treatment for SSD and AHL, clinical outcome measures in those studies and across CI centers vary greatly. Only with a consistent use of defined and agreed-upon outcome measures across centers can high-level evidence be generated to assess the safety and efficacy of CIs and alternative treatments in recipients with SSD and AHL. METHODS: This paper presents a comparative study design and minimum outcome measures for the assessment of current treatment options in patients with SSD/AHL. The protocol was developed, discussed, and eventually agreed upon by expert panels that convened at the 2015 APSCI conference in Beijing, China, and at the CI 2016 conference in Toronto, Canada. RESULTS: A longitudinal study design comparing CROS-HA, BCD, and CI treatments is proposed. The recommended outcome measures include (1) speech in noise testing, using the same set of 3 spatial configurations to compare binaural benefits such as summation, squelch, and head shadow across devices; (2) localization testing, using stimuli that rove in both level and spectral content; (3) questionnaires to collect quality of life measures and the frequency of device use; and (4) questionnaires for assessing the impact of tinnitus before and after treatment, if applicable. CONCLUSION: A protocol for the assessment of treatment options and outcomes in recipients with SSD and AHL is presented. The proposed set of minimum outcome measures aims at harmonizing assessment methods across centers and thus at generating a growing body of high-level evidence for those treatment options.

Tinnitus Suppression by Intracochlear Electrical Stimulation in Single-Sided Deafness: A Prospective Clinical Trial - Part I.

Cochlear implantation is a viable treatment option for tinnitus, but the underlying mechanism is yet unclear. Is the tinnitus suppression due to the reversal of the assumed maladaptive neuroplasticity or is it the shift in attention from the tinnitus to environmental sounds and therefore a reduced awareness that reduces tinnitus perception? In this prospective trial, 10 patients with single-sided deafness were fitted with a cochlear implant to investigate the effect of looped intracochlear electrical stimulation (i.e. stimulation that does not encode environmental sounds) on tinnitus, in an effort to find optimal stimulation parameters. Variables under investigation were: amplitude (perceived stimulus loudness), anatomical location inside the cochlea (electrode/electrodes), amplitude modulation, polarity (cathodic/anodic first biphasic stimulation) and stimulation rate. The results suggest that tinnitus can be reduced with looped electrical stimulation, in some cases even with inaudible stimuli. The optimal stimuli for tinnitus suppression appear to be subject specific. However, medium-to-loud stimuli suppress tinnitus significantly better than soft stimuli, which partly can be explained by the masking effect. Although the long-term effects on tinnitus would still have to be investigated and will be described in part II, intracochlear electrical stimulation seems a potential treatment option for tinnitus in this population.

Enhanced intensity discrimination in the intact ear of adults with unilateral deafness.

Physiological measures of neural activity in the auditory cortex have revealed plasticity following unilateral deafness. Central projections from the remaining ear reorganize to produce a stronger cortical response than normal. However, little is known about the perceptual consequences of this increase. One possibility is improved sound intensity discrimination. Intensity difference limens were measured in 11 individuals with unilateral deafness that were previously shown to exhibit increased cortical activity to sounds heard by the intact ear. Significantly smaller mean difference limens were observed compared with controls. These results provide evidence of the perceptual consequences of plasticity in humans following unilateral deafness.