Objective: 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.
Study Design: Prospective design.
Setting: Tertiary referral center; cochlear implant (CI) program.
Patients: 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.
Intervention: 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.
Main Outcome Measures: 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.
Results: 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.
Conclusion: 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.