[Audiological results with cochlear implants for single-sided deafness]. / Audiologische Ergebnisse mit Cochlear implant bei einseitiger Taubheit.

INTRODUCTION: Single-sided deafness has a strong impact on quality of life. Besides the difficulties in sound localization, patients also require increased effort to hear. The latter makes it difficult to follow conversations for an extended period, leading to social isolation. Cochlear implantation (CI) represents a possible treatment option for deafness in one ear. METHODS: In the present study, 13 patients with unilateral deafness where treated with CI. All patients were examined by pure tone audiometry and speech tests (Freiburger; HSM; OlSa), as well as sound localisations tests. The single-sided deaf situation is compared to CI-aided binaural hearing. RESULTS: At 100%, the acceptance rate was very high. The two different auditory inputs were well integrated. Patients reported satisfactory restoration of acoustic orientation and sound localization as well as great ease of listening in noisy surroundings. There was no negative impact on the normal hearing side. CONCLUSION: These preliminary results confirm the effectiveness of CI treatment in unilateral deafness.

Head shadow, squelch, and summation effects in bilateral users of the MED-EL COMBI 40/40+ cochlear implant.

OBJECTIVE: The aim of the study was to investigate the impact of bilateral cochlear implant use on speech perception in noise in bilateral users of the MED-EL COMBI 40/40+ cochlear implants. DESIGN: Speech reception thresholds were measured in 21 subjects using the Oldenburg sentence test. Speech was always presented from the front. Noise was either presented from the front, from the left side, or from the right side. Each condition was measured for unilateral and bilateral implant use. RESULTS: For three subjects, the test was too difficult to be administered. The 18 subjects from whom a complete data set could be obtained showed a significant head shadow effect and summation effect for all test conditions, whereas the squelch effect was significant for noise from the left side only. Average effect sizes were significant for all effects and amounted to 6.8 dB for the head shadow effect, 0.9 dB for the squelch effect, and 2.1 dB for the summation effect. Effect sizes were not correlated with duration of deafness. CONCLUSIONS: Bilateral cochlear implant users can at least qualitatively benefit from the effects that are known from normal-hearing subjects, that is, head shadow, summation, and squelch effect. Bilateral cochlear implantation also reduces the performance gap between cochlear implant users and normal-hearing subjects.

Sound localization in bilateral users of MED-EL COMBI 40/40+ cochlear implants.

OBJECTIVE: The purpose of the study was to investigate sound localization with bilateral and unilateral cochlear implants. DESIGN: Sound localization tests were performed on 20 bilaterally implanted MED-EL COMBI 40/40+ users. All subjects were bilaterally implanted during adolescence or later. Sound localization was tested in the frontal horizontal plane by using 9 equally spaced loudspeakers and speech-shaped noise bursts at randomized levels. RESULTS: The group of subjects who were bilaterally deafened after 5 to 6 yr of age (18 subjects) showed a statistically significant improvement in sound localization when using both implants, compared with when using only one. The mean deviation between the presentation azimuth and the response azimuth was 16.6 degrees when using both implants, which was on average 37.1 degrees smaller than when using one implant only. When adjusted for the localization error that was constant across loudspeakers, the mean deviation was 15.9 degrees for bilateral implant use, representing an improvement of 30.1 degrees over unilateral implant use. Statistical analysis showed that in this group, performance measures were not correlated with subject details such as age at onset of deafness or duration of unilateral implant use. In contrast, subjects who were bilaterally deafened before 6 yr of age (2 subjects) did not show a benefit in sound localization from bilateral implants. CONCLUSIONS: Bilateral cochlear implants offer a substantial benefit in sound localization to late-deafened, late-implanted subjects. The very limited data from early-deafened subjects implanted at a later age could suggest that these subjects may not benefit in sound localization from bilateral cochlear implants. It is possible that early implantation for early deafened subjects might allow better acquisition of spatial hearing, thus leading to improved localization performance.