Determining the Sample Size for Future Trials of Hearing Instruments for Unilaterally Deaf Adults: An Application of Network Meta-analysis.

OBJECTIVE: Previous trials have compared the efficacy of hearing instruments to no intervention in adults with single-sided deafness (SSD) or the relative efficacy of different instruments. Network meta-analysis (NMA) was used to refine estimates of effect sizes to determine required sample sizes for further trials. DATA SOURCES: PubMed, EMBASE, MEDLINE, Cochrane, CINAHL, and DARE databases were searched with no restrictions on language, with studies to February 2015 included. STUDY SELECTION: Studies were included that 1) assessed hearing instruments in adults with SSD; 2) compared instruments with other instruments, placebo, or no intervention; 3) measured speech perception in quiet/noise and listening ability; 4) were prospective controlled or observational studies. DATA EXTRACTION: The following data were extracted: sample size in each group, type of intervention and comparator, type of outcomes, mean outcome scores and their 95% confidence intervals. DATA SYNTHESIS: Random-effects meta-analysis was conducted to determine pooled effects for each outcome based on direct evidence alone. NMA used graph-theoretical method to determine pooled effects based on indirect evidence. Sample size calculations were conducted for each outcome for each class of evidence. CONCLUSIONS: The incorporation of indirect evidence had substantial impacts on some effect sizes but negligible impacts on other effects. The most notable impacts were on self-reported listening ability and measures of speech perception in noise. Changes in effect size estimates and required sample sizes resulting from the incorporation of indirect evidence highlight areas of uncertainty where trials may be feasible to conduct.

The psychological and social consequences of single-sided deafness in adulthood.

OBJECTIVES: This study examined the subjective psychological and social effects of highly asymmetric hearing loss (single-sided deafness [SSD]) in adults. DESIGN: Three group interviews were conducted using the critical incident technique and analysed using an inductive thematic analysis. STUDY SAMPLE: Eight adults with a clinical diagnosis of a moderately severe hearing loss or greater in one ear and normal or near-normal hearing in the other ear. RESULTS: A range of functional hearing difficulties associated with SSD including impaired speech in background noise and reduced spatial awareness were reported to affect social and psychological well-being. Social consequences of SSD resulted from activity limitations and participation restrictions including withdrawal from and within situations. Participants reported psychological effects including worrying about losing the hearing in their other ear, embarrassment related to the social stigma attached to hearing loss and reduced confidence and belief in their abilities to participate. CONCLUSIONS: Single-sided deafness can be associated with many negative consequences. Counselling may help overcome the psychological consequences of hearing loss regardless of whether technological support such as a hearing aid is prescribed. The audiological management of these individuals should support the development of listening strategies and set appropriate expectations for participation in everyday listening situations.

An Assessment of the Clinical Acceptability of Direct Acoustic Cochlear Implantation for Adults With Advanced Otosclerosis in the United Kingdom.

HYPOTHESIS: Assess the clinical acceptability of direct acoustic cochlear implantation for patients with advanced otosclerosis and the support for conducting a controlled trial of its effectiveness in the United Kingdom. BACKGROUND: Emerging evidence supports the efficacy of direct acoustic cochlear implantation in patients with advanced otosclerosis whose needs cannot be managed using the combination of stapes surgery and hearing aids. A controlled trial would provide evidence for its effectiveness and cost-effectiveness to healthcare commissioners. METHODS: An online survey of clinical professionals was constructed to characterize current standard of care for patients with advanced otosclerosis and to assess whether clinicians would be willing to refer patients into a trial to evaluate direct acoustic cochlear implantation. A consensus process was conducted to define inclusion criteria for the future trial. RESULTS: No survey respondent considered direct acoustic cochlear implantation to be inappropriate with a majority indicating that they would refer patients into a future trial. The consensus was that there is a lack of available treatment options for those patients with bone conduction thresholds worse than 55 dB HL and who did not meet current criteria for cochlear implantation. CONCLUSION: The present study confirms that a controlled trial to evaluate the effectiveness of direct acoustic cochlear implantation would have the support of clinicians in the United Kingdom. A feasibility study would be required to determine whether patients who meet the inclusion criteria could be recruited in a timely manner and in sufficient numbers to conduct a formal evaluation of effectiveness.

Hearing Instruments for Unilateral Severe-to-Profound Sensorineural Hearing Loss in Adults: A Systematic Review and Meta-Analysis.

OBJECTIVES: A systematic review of the literature and meta-analysis was conducted to assess the nature and quality of the evidence for the use of hearing instruments in adults with a unilateral severe to profound sensorineural hearing loss. DESIGN: The PubMed, EMBASE, MEDLINE, Cochrane, CINAHL, and DARE databases were searched with no restrictions on language. The search included articles from the start of each database until February 11, 2015. Studies were included that (a) assessed the impact of any form of hearing instrument, including devices that reroute signals between the ears or restore aspects of hearing to a deaf ear, in adults with a sensorineural severe to profound loss in one ear and normal or near-normal hearing in the other ear; (b) compared different devices or compared a device with placebo or the unaided condition; (c) measured outcomes in terms of speech perception, spatial listening, or quality of life; (d) were prospective controlled or observational studies. Studies that met prospectively defined criteria were subjected to random effects meta-analyses. RESULTS: Twenty-seven studies reported in 30 articles were included. The evidence was graded as low-to-moderate quality having been obtained primarily from observational before-after comparisons. The meta-analysis identified statistically significant benefits to speech perception in noise for devices that rerouted the speech signals of interest from the worse ear to the better ear using either air or bone conduction (mean benefit, 2.5 dB). However, these devices also degraded speech understanding significantly and to a similar extent (mean deficit, 3.1 dB) when noise was rerouted to the better ear. Data on the effects of cochlear implantation on speech perception could not be pooled as the prospectively defined criteria for meta-analysis were not met. Inconsistency in the assessment of outcomes relating to sound localization also precluded the synthesis of evidence across studies. Evidence for the relative efficacy of different devices was sparse but a statistically significant advantage was observed for rerouting speech signals using abutment-mounted bone conduction devices when compared with outcomes after preoperative trials of air conduction devices when speech and noise were colocated (mean benefit, 1.5 dB). Patients reported significant improvements in hearing-related quality of life with both rerouting devices and following cochlear implantation. Only two studies measured health-related quality of life and findings were inconclusive. CONCLUSIONS: Devices that reroute sounds from an ear with a severe to profound hearing loss to an ear with minimal hearing loss may improve speech perception in noise when signals of interest are located toward the impaired ear. However, the same device may also degrade speech perception as all signals are rerouted indiscriminately, including noise. Although the restoration of functional hearing in both ears through cochlear implantation could be expected to provide benefits to speech perception, the inability to synthesize evidence across existing studies means that such a conclusion cannot yet be made. For the same reason, it remains unclear whether cochlear implantation can improve the ability to localize sounds despite restoring bilateral input. Prospective controlled studies that measure outcomes consistently and control for selection and observation biases are required to improve the quality of the evidence for the provision of hearing instruments to patients with unilateral deafness and to support any future recommendations for the clinical management of these patients.

Benefits to Speech Perception in Noise From the Binaural Integration of Electric and Acoustic Signals in Simulated Unilateral Deafness.

OBJECTIVES: This study used vocoder simulations with normal-hearing (NH) listeners to (1) measure their ability to integrate speech information from an NH ear and a simulated cochlear implant (CI), and (2) investigate whether binaural integration is disrupted by a mismatch in the delivery of spectral information between the ears arising from a misalignment in the mapping of frequency to place. DESIGN: Eight NH volunteers participated in the study and listened to sentences embedded in background noise via headphones. Stimuli presented to the left ear were unprocessed. Stimuli presented to the right ear (referred to as the CI-simulation ear) were processed using an eight-channel noise vocoder with one of the three processing strategies. An Ideal strategy simulated a frequency-to-place map across all channels that matched the delivery of spectral information between the ears. A Realistic strategy created a misalignment in the mapping of frequency to place in the CI-simulation ear where the size of the mismatch between the ears varied across channels. Finally, a Shifted strategy imposed a similar degree of misalignment in all channels, resulting in consistent mismatch between the ears across frequency. The ability to report key words in sentences was assessed under monaural and binaural listening conditions and at signal to noise ratios (SNRs) established by estimating speech-reception thresholds in each ear alone. The SNRs ensured that the monaural performance of the left ear never exceeded that of the CI-simulation ear. The advantages of binaural integration were calculated by comparing binaural performance with monaural performance using the CI-simulation ear alone. Thus, these advantages reflected the additional use of the experimentally constrained left ear and were not attributable to better-ear listening. RESULTS: Binaural performance was as accurate as, or more accurate than, monaural performance with the CI-simulation ear alone. When both ears supported a similar level of monaural performance (50%), binaural integration advantages were found regardless of whether a mismatch was simulated or not. When the CI-simulation ear supported a superior level of monaural performance (71%), evidence of binaural integration was absent when a mismatch was simulated using both the Realistic and the Ideal processing strategies. This absence of integration could not be accounted for by ceiling effects or by changes in SNR. CONCLUSIONS: If generalizable to unilaterally deaf CI users, the results of the current simulation study would suggest that benefits to speech perception in noise can be obtained by integrating information from an implanted ear and an NH ear. A mismatch in the delivery of spectral information between the ears due to a misalignment in the mapping of frequency to place may disrupt binaural integration in situations where both ears cannot support a similar level of monaural speech understanding. Previous studies that have measured the speech perception of unilaterally deaf individuals after CI but with nonindividualized frequency-to-electrode allocations may therefore have underestimated the potential benefits of providing binaural hearing. However, it remains unclear whether the size and nature of the potential incremental benefits from individualized allocations are sufficient to justify the time and resources required to derive them based on cochlear imaging or pitch-matching tasks.

The developmental trajectory of spatial listening skills in normal-hearing children.

PURPOSE: To establish the age at which children can complete tests of spatial listening and to measure the normative relationship between age and performance. METHOD: Fifty-six normal-hearing children, ages 1.5-7.9 years, attempted tests of the ability to discriminate a sound source on the left from one on the right, to localize a source, to track moving sources, and to perceive speech in noise. RESULTS: Tests of left-right discrimination, movement tracking, and speech perception were completed by ≥ 75% of children older than 3 years. Children showed adult levels of performance from age 1.5 years (movement tracking), 3 years (left-right discrimination), and 6 years (localization and speech in noise). Spatial release from masking-calculated as the difference in speech reception thresholds between conditions with spatially coincident and spatially separate sp-eech and noise--remained constant at 5 dB from age 3 years. Data from a separate study demonstrate the age at which children with cochlear implants can complete the same tests. Assessments of left-right discrimination, movement tracking, and speech perception were completed by ≥ 75% of children who are older than 5 years and who wear cochlear implants. CONCLUSION: These data can guide the selection of tests for future studies and inform the interpretation of results from clinical populations.