Functional Result After Cochlear Implantation in Children and Adults With Single-sided Deafness :

A great deal of variability exists in the speech-recognition abilities of postlingually deaf adult cochlear implant (CI) recipients. A number of previous studies have shown that duration of deafness is a primary factor affecting CI outcomes; however, there is little agreement regarding other factors that may affect performance. The objective of the present study was to determine the source of variability in CI outcomes by examining three main factors, biographic/audiologic information, electrode position within the cochlea, and cognitive abilities in a group of newly implanted CI recipients. Participants were 114 postlingually deaf adults with either the Cochlear or Advanced Bionics CI systems. Biographic/audiologic information, aided sentence-recognition scores, a high resolution temporal bone CT scan and cognitive measures were obtained before implantation. Monosyllabic word recognition scores were obtained during numerous test intervals from 2 weeks to 2 years after initial activation of the CI. Electrode position within the cochlea was determined by three-dimensional reconstruction of pre- and postimplant CT scans. Participants' word scores over 2 years were fit with a logistic curve to predict word score as a function of time and to highlight 4-word recognition metrics (CNC initial score, CNC final score, rise time to 90% of CNC final score, and CNC difference score). Participants were divided into six outcome groups based on the percentile ranking of their CNC final score, that is, participants in the bottom 10% were in group 1; those in the top 10% were in group 6. Across outcome groups, significant relationships from low to high performance were identified. Biographic/audiologic factors of age at implantation, duration of hearing loss, duration of hearing aid use, and duration of severe-to-profound hearing loss were significantly and inversely related to performance as were frequency modulated tone, sound-field threshold levels obtained with the CI. That is, the higher-performing outcome groups were younger in age at the time of implantation, had shorter duration of severe-to-profound hearing loss, and had lower CI sound-field threshold levels. Significant inverse relationships across outcome groups were also observed for electrode position, specifically the percentage of electrodes in scala vestibuli as opposed to scala tympani and depth of insertion of the electrode array. In addition, positioning of electrode arrays closer to the modiolar wall was positively correlated with outcome. Cognitive ability was significantly and positively related to outcome; however, age at implantation and cognition were highly correlated. After controlling for age, cognition was no longer a factor affecting outcomes. There are a number of factors that limit CI outcomes. They can act singularly or collectively to restrict an individual's performance and to varying degrees. The highest performing CI recipients are those with the least number of limiting factors. Knowledge of when and how these factors affect performance can favorably influence counseling, device fitting, and rehabilitation for individual patients and can contribute to improved device design and application.

Up to now, treatment modalities of unilateral deafness consist of no treatment, conventional contralateral routing of signal (CROS), or Bone-Anchored Hearing Aid (BAHA) hearing aid. Cochlear implantation makes a new treatment modality available for patients with single-sided deafness. The aim of this study is to evaluate the use of unilateral electrical stimulation with normal hearing on the contralateral side after a period of 6 months compared with the preoperative unaided situation, conventional CROS, or BAHA hearing aids. Prospective design. Tertiary referral center; cochlear implant (CI) program. Eleven adult subjects with unilateral deafness of various causes were enrolled in the study. Only those patients were included in whom therapy with CROS hearing aid or BAHA was not successful and in whom the auditory nerve was found to be intact and the cochlea patent for cochlear implantation. All subjects were fitted in random order with a BAHA Intenso mounted on the softband/tension clamp or with a CROS hearing aid. After test periods with both devices, the subjects received a CI. The Hochmair-Schulz-Moser sentence test and the Oldenburg sentence test were used to test speech comprehension in 3 presentation configurations in the unaided situation, with conventional CROS and BAHA hearing aids before cochlear implantation as well as after 6 months with CI. Localization was assessed using an array of 7 speakers at head level in a frontal semicircle. Subjective improvement in daily life was evaluated using the Speech, Spatial and Qualities of Hearing Scale, the Health Utilities Index 3 and the International Outcome Inventory for Hearing Aids questionnaires. Tinnitus distress was measured with a tinnitus scale before and after CI implantation. The results show significant improvement in localization ability as well as in speech comprehension in most presentation configurations with the CI. Especially, there is no negative effect on speech comprehension if the noise is presented to the CI ear and speech to the normal hearing ear. With the CI, the summation and squelch effects are not significant, but a significant combined head shadow effect is seen. Speech, Spatial and Qualities of Hearing results show an overall benefit of wearing the CI compared with the other treatment options. The tinnitus scale revealed a positive effect of CI stimulation in cases of preoperative tinnitus. The results in these patients suggest that cochlear implantation improves hearing abilities in people with single-sided deafness and is superior to the alternative treatment options. The use of the CI does not interfere with speech understanding in the normal hearing ear. Our data suggest that the binaural integration of electric and acoustic stimulation is possible even with unilateral normal hearing.

This pilot study examined speech recognition, localization, temporal and spectral discrimination, and subjective reports of cochlear implant (CI) recipients with unilateral deafness. Three adult male participants with short-term unilateral deafness (<5 yr) participated. All had sudden onset of severe-to-profound hearing loss in 1 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). All participants had open-set speech recognition and excellent audibility (250-6,000 Hz) with the CI. Localization improved bilaterally compared with the NH ear alone. Word recognition in noise was significantly better bilaterally than with the NH ear for 2 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 2 participants and spectral difference discrimination for all participants. Participants wore the CI full time, and subjective reports were positive. 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.