Partial deafness cochlear implantation (PDCI) and electric-acoustic stimulation (EAS).

The purposes of this paper are to (1) review briefly the experience to date with combined EAS for patients with some residual, low-frequency hearing; and (2) describe the further results that have been obtained with this combination for patients with higher levels of residual hearing at low frequencies, termed 'PDCI'. In broad terms, PDCI and combined EAS have produced large improvements in the speech reception abilities of the treated patients, compared with preoperative scores or with postoperative scores for electric stimulation only or acoustic stimulation only. The benefits have been especially large for recognition of speech presented in competition with interfering sounds such as speech-spectrum noise. Although PDCI and combined EAS have been established as highly effective procedures, questions remain about optimal combinations of electric and acoustic stimuli; the ideal depth of insertion for the electrode array; whether the ideal depth may vary from patient to patient; and whether the reliability of hearing preservation in an implanted cochlea can be increased beyond the present high levels. The answers to these questions could lead to even better treatments for persons with little or no hearing at high frequencies and at least some remaining hearing at low frequencies.