Superiority of bilateral cochlear implantation over unilateral cochlear implantation in tone discrimination in Chinese patients

Purpose: The benefits of bilateral cochlear implants (Cis) versus unilateral Cis were evaluated by comparing the Cantonese lexical tone discrimination scores conducted in a quiet environment and against a background noise. Materials and Methods: Four postlingually deafened Cantonese-speaking adults (2 men and 2 women) with bilateral Cis were included in this study. The subjects were their own control in the monaural hearing condition. Both the Cantonese lexical tone stimuli and the speech-weighted background noise were presented at 0degrees azimuth and at a distance of 1 m from the subject. The speech stimuli, which were maintained at 65 dB sound pressure level, were presented, in both a quiet environment and against a background noise at signal to noise ratios (SNRs) of +15, +10, +5, 0, -5, -10, and -15. Results: Against a background noise, the bilateral Cis required +5 dB SNR only to obtain significant scores in discriminating Cantonese lexical tones and to achieve discrimination scores that were comparable to the optimal discrimination scores obtained in quiet. No significant difference in the discrimination scores was observed between binaural and monaural hearing conditions when the tests were conducted in quiet. Conclusions: Our study showed that in the presence of background noise, bilateral Cis were better than unilateral Cis in discriminating Cantonese lexical tones.