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EXPECTATIONS AND CHOICE OF ELECTRODE FOR CI CANDIDATES WITH SIGNIFICANT LOW-FREQUENCY RESIDUAL HEARING

Bernard Fraysse1, Chris James1,2, Olivier Deguine1, Olivier Sterkers3, Didier Bouccara3, Alain Robier4

1Hôpital Purpan, Toulouse, France/2Cochlear France, Toulouse, France/3AP-HP Hôpital Beaujon, Clichy, France/4Hôpital Bretonneau, Tours, France

■ OBJECTIVES: Many candidates for cochlear implantation within “expanded” indications will have significant low-frequency residual hearing coupled with thresholds which exceed 90dB in the mid to high frequencies; thereby depriving them of information important for understanding speech. Over recent years “Hybrid” or “electro-acoustic” stimulation has been proposed which allows the combined benefits of electric and acoustic stimulation in the implanted ear, such as greatly improved speech recognition in noise. One question currently under discussion is: Would shorter electrodes provide equivalent performance to standard “long” electrodes if hearing was lost? We hypothesised that the performance of candidates for “short” electrode is biased compared to those who would at present receive a “long” electrode. As well, a basis for the choice of electrode based upon audiometric and radiological characteristics was developed.

■ METHOD: A retrospective analysis was performed upon data from a study of hearing conservation and speech recognition for 31 patients implanted with Nucleus 24 Contour Advance. 13/31 had pre-operative thresholds 60dBHL at 500Hz and classed as candidates for a “short” electrode according to clinical trial criteria. Correlations were computed between thresholds and speech recognition scores.

■ RESULTS: Mean increases in speech recognition were 42%age points in quiet and 51%age points in 10dBSNR noise. Notably, the 13 patients classed as “short” electrode candidates had pre-operatively significantly greater speech recognition in noise (mean 27% vs 10%) compared to the “long” candidates, with a trend for greater scores for words presented in quiet (29% vs 17%). However, post-operatively there were no significant differences in performance between the two groups. There were no significant correlations between recognition scores and acoustic thresholds, pre- and post-operatively.

■ CONCLUSIONS: Cochlear implantation gave substantial speech recognition benefit in this group of marginal candidates whether or not residual hearing was preserved. There was no overall difference observed in outcomes for “short” electrode candidates who received the same standard electrode as “long” electrode candidates. Therefore differences in mean performance between populations of“long” and “short” electrode users can be attributed to the type of electrode. The authors propose that electrodes should be “as long aspossible” balanced against success in conserving residual hearing.