CI can successfully be used as treatment of severe tinnitus in patients with single-sided deafness and is equally effective for pure tone, narrow band noise, and polyphonic tinnitus. Long-term results show that implantation provides durable tinnitus relief in these patients. These results support the hypothesis that physiopathological mechanisms after peripheral deafferentation are reversible when hearing is restored. Single-sided deafness accompanied by severe tinnitus is a new indication for CI.

The value of cochlear implants (CI) in patients with profound unilateral hearing loss (UHL) and tinnitus has recently been investigated. The authors previously demonstrated the feasibility of CI in a 12- month outcome study in a prospective UHL cohort. The aim of this study was to investigate the binaural auditory outcomes in this cohort 36 months after CI surgery. The 36-month outcome was evaluated in 22 CI users with postlingual UHL and severe tinnitus. Twelve subjects had contralateral normal hearing (single-sided deafness - SSD group) and 10 subjects had a contralateral, mild to moderate hearing loss and used a hearing aid (asymmetric hearing loss - AHL group). Speech perception in noise was assessed in two listening conditions: the CI_off and the CI_on condition. The binaural summation effect (S₀N₀), binaural squelch effect (S₀N_CI) and the combined head shadow effect (S_CIN₀) were investigated. Subjective benefit in daily life was assessed by means of the Speech, Spatial and Qualities of Hearing Scale (SSQ). At 36 months, a significant binaural summation effect was observed for the study cohort (2.00, SD 3.82 dB; p < 0.01) and for the AHL subgroup (3.34, SD 5.31 dB; p < 0.05). This binaural effect was not significant 12 months after CI surgery. A binaural squelch effect was significant for the AHL subgroup at 12 months (2.00, SD 4.38 dB; p < 0.05). A significant combined head shadow and squelch effect was also noted in the spatial configuration S_CIN₀ for the study cohort (4.00, SD 5.89 dB; p < 0.01) and for the AHL subgroup (5.67, SD 6.66 dB; p < 0.05). The SSQ data show that the perceived benefit in daily life after CI surgery remains stable up to 36 months at CI_on. CI can significantly improve speech perception in noise in patients with UHL. The positive effects of CI_on speech perception in noise increase over time up to 36 months after CI surgery. Improved subjective benefit in daily life was also shown to be sustained in these patients.

Unilateral tinnitus can significantly decrease speech reception in noise in the nontinnitus ear.

Background: Recently, a new speech coding strategy named ‘fine structure processing’ (FSP) has been launched. Methods: 32 subjects, all users of the MED-EL PULSARCI¹⁰⁰ system, have been switched over from a TEMPO+ to an OPUS 2 speech processor. In 22 subjects, the FSP strategy could be implemented (FSP group), in 10 patients not (high-definition continuous interleaved sampling, HDCIS, group). Subjects were tested with the Tempo+ (CIS+) just before switch-over and after 12 months of OPUS 2 (FSP/HDCIS) use. Performance with FSP/HDCIS was tested at switch-over, and after 1, 3, 6 and 12 months. A sentence-in-noise test and a Speech Spatial and Qualities of Hearing Scale (SSQ) questionnaire were assessed at each test interval. Results: In the FSP group, the speech reception threshold shows a deterioration of 3.3 dB (n.s.) at the acute switch-over interval, but a significant improvement over time (p < 0.001) with a final benefit of 6.5 dB after 12 months of FSP use. A significant improvement over time can also be seen on the spatial subscore of the SSQ questionnaire (p = 0.009). No significant differences could be seen in the HDCIS group. Conclusion: The results show that by enhancing fine structure coding in the lower frequencies, as implemented in the FSP coding strategy, speech perception in noise can be enhanced.

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The relationship between the place of electrical stimulation from a cochlear implant and the corresponding perceived pitch remains uncertain. Previous studies have estimated what the pitch corresponding to a particular location should be. However, perceptual verification is difficult because a subject needs both a cochlear implant and sufficient residual hearing to reliably compare electric and acoustic pitches. Additional complications can arise from the possibility that the pitch corresponding to an electrode may change as the auditory system adapts to a sound processor. In the following experiment, five subjects with normal or near-to-normal hearing in one ear and a cochlear implant with a long electrode array in the other ear were studied. Pitch matches were made between single electrode pulse trains and acoustic tones before activation of the speech processor to gain an estimate of the pitch provided by electrical stimulation at a given insertion angle without the influence of exposure to a sound processor. The pitch matches were repeated after 1, 3, 6, and 12 months of experience with the sound processor to evaluate the effect of adaptation over time. Pre-activation pitch matches were lower than would be estimated by a spiral ganglion pitch map. Deviations were largest for stimulation below 240° degrees and smallest above 480°. With experience, pitch matches shifted towards the frequency-to-electrode allocation. However, no statistically significant pitch shifts were observed over time. The likely explanation for the lack of pitch change is that the frequency-to-electrode allocations for the long electrode arrays were already similar to the pre-activation pitch matches. Minimal place pitch shifts over time suggest a minimal amount of perceptual remapping needed for the integration of electric and acoustic stimuli, which may contribute to shorter times to asymptotic performance.

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