A monosyllabic word test was administered to 114 postlingually-deaf adult cochlear implant (CI) recipients at numerous intervals from two weeks to two years post-initial CI activation. Biographic/audiologic information, electrode position, and cognitive ability were examined to determine factors affecting CI outcomes. Results revealed that Duration of Severe-to-Profound Hearing Loss, Age at Implantation, CI Sound-field Threshold Levels, Percentage of Electrodes in Scala Vestibuli, Medio-lateral Electrode Position, Insertion Depth, and Cognition were among the factors that affected performance. Knowledge of how factors affect performance can influence counseling, device fitting, and rehabilitation for patients and may contribute to improved device design.

Using the protocol outlined in this study, it is possible to reliably record EAP responses from most subjects and for most electrodes in Nucleus CI24M cochlear implant users. These responses are robust and recording these responses does not require that the subject sleep or remain still. Based on these results, a specific protocol is proposed for measurement of the EAP using the NRT system of the CI24M cochlear implant. Potential clinical implications of these results are discussed.

Speech perception measures used with cochlear implant candidates and recipients should reflect the listening challenges that individuals encounter in natural communication situations. These data provide the basis for recommending new candidacy criteria based on speech recognition tests presented at 60 and/or 50 dB SPL, intensity levels that reflect real-life listening, rather than 70 dB SPL.

These results support a growing consensus that bilateral implantation provides functional benefits beyond those of unilateral implantation. Longitudinal data suggest that some aspects of binaural processing continue to develop up to 1 yr after implantation. The squelch effect, often reported as absent or rare in previous studies of bilateral cochlear implantation, was present for most subjects at the 1 yr measurement interval.

Objective This pilot study examined speech recognition, localization, temporal and spectral discrimination and subjective reports of cochlear implant (CI) recipients with unilateral deafness. Study Design Three adult males with short-term unilateral deafness (< 5 years) participated. All had sudden onset of severe to profound hearing loss in one ear, which then received a CI, and normal or near normal hearing in the other ear. Speech recognition in quiet and noise, localization, discrimination of temporal and spectral cues and a subjective questionnaire were obtained over several days. Listening conditions were CI, normal hearing (NH) ear, and bilaterally (CI and NH). Results All participants had open-set speech recognition and excellent audibility (250–6000 Hz) with the CI. Localization improved bilaterally compared to the NH ear alone. Word recognition in noise was significantly better bilaterally than with the NH ear for two participants. Sentence recognition in various noise conditions did not show significant bilateral improvement; however, the CI did not hinder performance in noise even when noise was toward the CI side. The addition of the CI improved temporal difference discrimination for two participants and spectral difference discrimination for all participants. Participants wore the CI full time and subjective reports were positive. Conclusion Overall, the CI recipients with unilateral deafness obtained open-set speech recognition, improved localization, improved word recognition in noise, and improved perception of their ability to hear in everyday life. A larger study is warranted to further quantify the benefits and limitations of cochlear implantation in individuals with unilateral deafness.

Objective Bilateral severe-to-profound sensorineural hearing loss is a standard criterion for cochlear implantation. Increasingly, patients are implanted in one ear and continue to use a hearing aid in the non-implanted ear to improve abilities such as sound localization and speech understanding in noise. Patients with severe-to-profound hearing loss in one ear and a more moderate hearing loss in the other ear (i.e., asymmetric hearing) are not typically considered candidates for cochlear implantation. Amplification in the poorer ear is often unsuccessful due to limited benefit, restricting the patient to unilateral listening from the better ear alone. The purpose of this study was to determine if patients with asymmetric hearing loss could benefit from cochlear implantation in the poorer ear with continued use of a hearing aid in the better ear. Design Ten adults with asymmetric hearing between ears participated. In the poorer ear, all participants met cochlear implant candidacy guidelines; seven had postlingual onset and three had pre/perilingual onset of severe-to-profound hearing loss. All had open-set speech recognition in the better hearing ear. Assessment measures included word and sentence recognition in quiet, sentence recognition in fixed noise (four-talker babble) and in diffuse restaurant noise using an adaptive procedure, localization of word stimuli and a hearing handicap scale. Participants were evaluated pre-implant with hearing aids and post-implant with the implant alone, the hearing aid alone in the better ear and bimodally (the implant and hearing aid in combination). Postlingual participants were evaluated at six months post-implant and pre/perilingual participants were evaluated at six and 12 months post-implant. Data analysis compared results 1) of the poorer hearing ear pre-implant (with hearing aid) and post-implant (with cochlear implant), 2) with the device(s) used for everyday listening pre- and post-implant and, 3) between the hearing aid-alone and bimodal listening conditions post-implant. Results The postlingual participants showed significant improvements in speech recognition after six months cochlear implant use in the poorer ear. Five postlingual participants had a bimodal advantage over the hearing aid-alone condition on at least one test measure. On average, the postlingual participants had significantly improved localization with bimodal input compared to the hearing aid-alone. Only one pre/perilingual participant had open-set speech recognition with the cochlear implant. This participant had better hearing than the other two pre/perilingual participants in both the poorer and better ear. Localization abilities were not significantly different between the bimodal and hearing aid-alone conditions for the pre/perilingual participants. Mean hearing handicap ratings improved post-implant for all participants indicating perceived benefit in everyday life with the addition of the cochlear implant. Conclusions Patients with asymmetric hearing loss who are not typical cochlea...

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We studied activation magnitudes in core, belt, and parabelt auditory cortex in adults with normal hearing (NH) and unilateral hearing loss (UHL) using an interrupted, single-event design and monaural stimulation with random spectrographic sounds. NH patients had one ear blocked and received stimulation on the side matching the intact ear in UHL. The objective was to determine whether the side of deafness affected lateralization and magnitude of evoked blood oxygen level-dependent responses across different auditory cortical fields (ACFs). Regardless of ear of stimulation, NH showed larger contralateral responses in several ACFs. With right ear stimulation in UHL, ipsilateral responses were larger compared to NH in core and belt ACFs, indicating neuroplasticity in the right hemisphere. With left ear stimulation in UHL, only posterior core ACFs showed larger ipsilateral responses, suggesting that most ACFs in the left hemisphere had greater resilience against reduced crossed inputs from a deafferented right ear. Parabelt regions located posterolateral to core and belt auditory cortex showed reduced activation in UHL compared to NH irrespective of RE/LE stimulation and lateralization of inputs. Thus, the effect in UHL compared to NH differed by ACF and ear of deafness.