gms | German Medical Science

Conclusion: After the initial use of several 8 channel maps over 8 months, all 14 CI recipients benefited from stimulation over the entire length of the electrode array covering two cochlea turns.

Objectives: In a prospective study we evaluated long-term effects of electrical stimulation of the apical region of the cochlea on speech perception, by using different channel arrangements.

Methods: Fourteen newly implanted subjects with a MED EL cochlear implant and a fully inserted (>30 mm) standard electrode array participated in the study. Four different electrode configurations had been defined for the 12-electrode array: (A) 8 most apical electrodes only (apical 8), B) 8 most basal electrodes only (basal 8), C) 8 electrodes spread across the whole array (spread 8), D) all 12 electrodes (full 12). The study followed an ABCABCD crossover design with one month familiarization with every condition prior to evaluation, after an initial 3-months period for the first condition. Tests included Freiburg monosyllables, vowels, consonants, and HSM sentences in quiet and in noise. Additionally, a pitch scaling test was performed at each interval.

Results: Based on the number of speech tests with the respective highest score, eight subjects achieved their best scores with full 12. Three subjects performed best with basal 8. Two subjects had their best scores with spread 8, and one subject performed about equally well with these three conditions. Speech perception with apical 8 was worse than with the other three conditions. The benefit from the de-activation of apical electrodes seems to correlate with pitch ambiguities in the apical region. Three out of the 6 patients with pitch reversals in the apical area performed best with basal-8. In addition they tested a spread 10 condition with two additional apical electrodes and chose this as preferred condition.

In order to eliminate the influence of channel number, we compared only basal 8 with spread-8. Again, eleven out of 14 subjects scored better with spread 8 which provided apical stimulation. At the end of the study, 11 subjects chose a full-12 map and 3 subjects chose 10-channel maps, i.e. basal 8 plus 2 apical electrodes.