Cochlear implantation in recipients with single-sided deafness: Audiological performance

Objective: To examine the auditory benefit of cochlear implants (CI) in patients with single-sided deafness (SSD).

Material and methods: Twenty patients with a normal pure tone audiogram (n?=?8) or moderate hearing loss (n?=?12) in one ear and a CI system MED-EL SONATA/CONCERTO?+?OPUS2 (n?=?12), COCHLEAR CI24RE(ST)?+?CP810 (n?=?7) and Advanced Bionics HiRes90?K?+?Harmony (n?=?1) in the contralateral ear and with at least 6 months of CI experience were tested with respect to directional hearing, speech perception in noise, binaural loudness matching, and binaural pitch matching. Twenty-six normal hearing controls were included for normative reference.

Results: Addition of the CI significantly improves directional hearing (percentage of correct source identifications improved from 14.9 to 15.6%, root mean square error decreased from 125 to 93°) and improves speech perception in noise (speech perception threshold median improved from ?2.3 to ?6.0?dB signal to noise ratio, equivalent to a binaural intelligibility level difference?=?3.7?dB). Alternate binaural loudness balancing showed that matching takes place at levels between 48 and 55?dB HL (group averages). In the pitch matching experiment, the standard deviation of the relative interaural frequency difference at 500, 1000, and 2000?Hz was 24.5, 22.8, and 24.0%, respectively (compared to 11.7, 14.4, and 12.3% in the control group).

Conclusions: In SSD, cochlear implantation considerably improves audiological performance in terms of directional hearing, binaural signal equivalence, and speech perception.