Natural history of contralateral residual hearing in binaural-bimodal hearing

The range of evaluation tools used in deciding which ear to implant and which to designate for a hearing aid (HA) should be expanded to include additional aspects to those tested by audiometry and basic speech perception. Residual hearing in non-implanted ears remains stable for at least 3 years after unilateral cochlear implantation, but regular refitting and monitoring of the HA function combined with cochlear implant (CI) mapping are mandatory for maximizing benefit from binaural-bimodal hearing.

To examine whether the clinical decision-making tools currently used to assess hearing are reliable guides when choosing the preferred ear for CI, and to determine the rate of residual hearing deterioration in the non-implanted ear over 36 months post-CI as a guide to recommending subsequent continued use of a contralateral HA as opposed to CI.

This was a retrospective evaluation of patients' charts. The pre-CI choice of the ear for implantation in a group of 37 binaural-bimodal users was re-evaluated. In a second group of 22 patients, residual hearing deterioration was followed for 36 months post-implantation.

In the group of 37 patients, subjective identification of the worse-hearing ear was in agreement with audiometric results in 28 cases, but disagreed with the unaided audiometric results in the other 9. Mean threshold values for the group of 22 patients remained stable over 36 months post-CI, except for the aided threshold at 4.0 kHz, which deteriorated by 10.9 dB (p=0.003).