Comparison of continuous interleaved sampling and simultaneous analog stimulation speech processing strategies in newly implanted adults with a Clarion 1.2 cochlear implant.
OBJECTIVE: This study consisted of a within-subjects comparison of speech recognition and patient preference when subjects used two different cochlear implant speech processing strategies with a Clarion 1.2 (enhanced bipolar) device: Simultaneous Analog Stimulation (SAS), and Continuous Interleaved Sampling (CIS). These two strategies used two different electrode configurations: the SAS strategy used bipolar stimulation, whereas the CIS strategy used monopolar stimulation. STUDY DESIGN: This was a multicenter study that used a within-subjects balanced crossover design. Experience with the two strategies was replicated in each subject using an ABAB design. Order of strategy use was balanced across all subjects. SETTING: The study was carried out at several cochlear implant centers affiliated with tertiary medical centers. PATIENTS: Subjects consisted of 25 postlingually deafened adults who received a Clarion cochlear implant. INTERVENTIONS: Total involvement by each subject was 14 weeks. Speech perception testing and sound quality assessments were performed after use with each strategy. MAIN OUTCOME MEASURES: Primary outcome measures include speech perception data and patient responses to questionnaires regarding speech and sound quality. RESULTS: Analyses revealed that performance did not differ significantly by the strategy encountered first as relative to the strategy encountered second and that the order in which a strategy was used did not appear to affect subjects' eventual preference for a particular strategy. Although speech recognition scores tended to be higher for CIS for most of the test measures at most of the test intervals, the analysis of variance to evaluate differences in strategy did not reveal a significant effect of strategy. Further analysis of scores obtained at the replication interval, however, revealed that scores obtained with CIS were significantly higher than scores obtained with SAS on the Hearing in Noise Test sentences in quiet and noise. In addition, significantly more patients indicated a final preference for the CIS strategy than for the SAS strategy. Importantly, both the analysis evaluating order and the analysis evaluating strategy revealed significant effects of evaluation period, indicating that time/experience with the implant had a significant effect on scores for each strategy, regardless of the order in which it was used (first or second). CONCLUSIONS: This study demonstrates that important learning occurs during the first several weeks of cochlear implant use, making it difficult to adequately compare performance with different speech processing strategies. However, the finding that patients often prefer the strategy they understand speech the best with supports the clinical practice of letting adult patients select their preferred strategy without formally evaluating speech perception with each available strategy.