Objective assessment of electrode discrimination with the auditory change complex in adult cochlear implant users.

The spatial auditory change complex (ACC) is a cortical response elicited by a change in place of stimulation. There is growing evidence that it provides a useful objective measure of electrode discrimination in cochlear implant (CI) users. To date, the spatial ACC has only been measured in relatively experienced CI users with one type of device. Early assessment of electrode discrimination could allow auditory stimulation to be optimized during a potentially sensitive period of auditory rehabilitation. In this study we used a direct stimulation paradigm to measure the spatial ACC in both pre- and post-lingually deafened adults. We show that it is feasible to measure the spatial ACC in different CI devices and as early as 1 week after CI switch-on. The spatial ACC has a strong relationship with performance on a behavioural discrimination task and in some cases provides information over and above behavioural testing. We suggest that it may be useful to measure the spatial ACC to guide auditory rehabilitation and improve hearing performance in CI users.

Developing an assessment approach for perceptual changes to tinnitus sound characteristics for adult cochlear implant recipients.

OBJECTIVE: To investigate the impact of cochlear implantation on tinnitus suppression, characteristics, localization, and duration. DESIGN: A cochlear implant (CI) recipient-focused postal questionnaire survey. STUDY SAMPLE: The questionnaire was posted, with consent, to 100 adults who had received a unilateral CI at the RNTNEH between 1988 and 1999. All adults spoke English as their first language and were postlingually deafened. Sixty-eight adults (38 female, 29 male, one unspecified) aged 31-80 years (mean 61 years) completed and returned the questionnaire without interview. RESULTS: With the processor 'ON', CI recipients experienced total or partial suppression of tinnitus ipsilateral to their CI in 57% of cases, and in 43% where tinnitus was perceived contralateral to the CI. The percentage of CI recipients who experienced high tone tinnitus was reduced from 60% pre-implant to 29% post-implant with the processor 'ON' while pulsatile tinnitus was reduced from 38% pre-implant to 13% post-implant. CIs were also found to reduce the tonal complexity and duration, and change the source localization of tinnitus post-implantation. CONCLUSIONS: Perceptual changes to tinnitus can take place post-implantation. Changes can occur within the four categories explored: tinnitus suppression, characteristics, localization, and duration of awareness per day.

Clinical use of electrode differentiation to enhance programming of cochlear implants.

The effect of deactivating indiscriminable cochlear implant (CI) electrodes for unilaterally implanted adults was evaluated using the BKB (Bamford-Kowal-Bench) sentence test in quiet and in pink noise (signal-to-noise ratio of +10dBA) and the adaptive Coordinate Response Measure (CRM). Each CI recipient who failed electrode differentiation (ED) in at least one electrode-pair, based on results of a pure-tone pitch-ranking task received two research programmes to try out in a cross-over study. Research programmes (RP) either employed discriminable electrodes only or the most discriminable two-thirds of the electrodes in the electrode array for CI recipients failing ED for more than a third of the electrodes. The participants were also asked to subjectively report improvement of or decline in sound quality in everyday listening situations. There was significant improvement in CRM speech reception thresholds (SRTs) (Z = -3.24, N = 15, P = 0.001), BKB sentence scores in quiet (t = 3.17, df = 24, P < 0.005) and also in pink noise (t = 2.26, df = 19, P < 0.005) after deactivating indiscriminable electrodes.

Benefits of the HiRes 120 coding strategy combined with the Harmony processor in an adult European multicentre study.

CONCLUSION: The Harmony processor was found to be reliable, comfortable and offered a substantially increased battery life compared with the previous generation processor. No significant improvement in speech understanding with HiRes was demonstrated from objective measures, but the majority of subjects showed a clear subjective preference for the combination HiRes 120/Harmony processor. OBJECTIVES: To evaluate experience with the Harmony™ sound processor, together with the HiRes 120 strategy. METHODS: Postlingually deafened adults implanted with a CII or HiRes 90K were included and divided into three groups: (1) experienced users using the Platinum body-worn processor; (2) experienced users who had been using other processors; (3) new users with the Harmony processor from first fitting. The latter group entered a randomized crossover protocol where half were initially fitted with HiRes and half with HiRes 120. The initial strategy was used for 3 months and the alternative for a further 3 months. Speech perception tests and questionnaires were performed. RESULTS: The study included 65 subjects. Implementing HiRes 120 was straightforward. The speech test group results did not show significant differences between HiRes and HiRes 120. However, the questionnaires showed significantly higher ratings for HiRes 120 in some instances. Subjects were highly satisfied with the Harmony processor.

Taste change following cochlear implantation.

Taste change is a well documented but under emphasised complication of middle ear surgery and is usually related to damage to the chorda tympani nerve (CTN). However, the taste outcomes following cochlear implantation have not been previously recorded. One hundred and forty one patients who had received cochlear implants between January 1997 and April 2006 were questioned using a postal survey regarding changes in the sense of taste following cochlear implantation. Sixty seven per cent of questionnaires were returned. Forty three patients (45%) experienced changes in taste following their surgery. Eighteen patients (19%) said that their symptoms had not resolved by the end of the follow up period (mean 51 months). CTN division produced taste change in 86%. Fifty per cent of patients who had CTN preservation developed taste change, presumably related to occult trauma to the nerve. The difference in the number of patients describing taste change in the two groups was statistically significant (p < 0.05). Resolution of symptoms took a mean of 20 weeks. For those patients in whom taste change was noted, resolution of symptoms was more likely if the CTN was divided rather than preserved although the difference was not statistically significant (p < 0.5). This may reflect neuronal injury during surgery which then fails to heal normally. These results are comparable to taste outcomes in patients undertaking middle ear surgery for non-inflammatory disease such as stapedectomy. The symptoms can be extremely troublesome and may not resolve with time. Careful consideration of the CTN intra-operatively is recommended and in the event of injury, the taste outcome may be better if the nerve is divided rather than left in situ but damaged. These findings have significant implications for patients as bilateral implantation becomes more commonplace.

Evaluation of bilaterally implanted adult subjects with the nucleus 24 cochlear implant system.

OBJECTIVE: To evaluate the speech perception benefits of bilateral implantation for subjects who already have one implant. STUDY DESIGN: Repeated measures. PATIENTS: Thirty adult cochlear implant users who received their second implant from 1 to 7 years with a mean of 3 years after their first device. Ages ranged from 29 to 82 years with a mean of 57 years. SETTING: Tertiary referral centers across the United Kingdom. MAIN OUTCOME MEASURES: Monosyllabic consonant-nucleus-consonant words and City University of New York sentences in quiet with coincident speech and noise and with the noise spatially separated from the speech by +/-90 degrees . RESULTS: At 9 months, results showed the second ear in noise was 13.9 +/- 5.9% worse than the first ear (p < 0.001); a significant binaural advantage of 12.6 +/- 5.4% (p < 0.001) over the first ear alone for speech and noise from the front; a 21 +/- 6% (p < 0.001) binaural advantage over the first ear alone when noise was ipsilateral to the first ear; no binaural advantage when noise was contralateral to the first ear. CONCLUSIONS: There is a significant bilateral advantage of adding a second ear for this group. We were unable to predict when the second ear would be the better performing ear, and by implanting both ears, we guarantee implanting the better ear. Sequential implantation with long delays between ears has resulted in poor second ear performance for some subjects and has limited the degree of bilateral benefit that can be obtained by these users. The dual microphone does not provide equivalent benefit to bilateral implants.