Nucleus 24 advanced encoder conversion study: performance versus preference.

OBJECTIVE: The Nucleus 24 Advanced Encoder Conversion Study was designed to determine the safety and effectiveness of the advanced combination encoder (ACE) and continuous interleaved sampling (CIS) speech coding strategies compared with that of the spectral peak (SPEAK) strategy in a large sample of postlinguistically deaf adults. Data from this study were analyzed to test the hypothesis that the group of subjects who prefer a given strategy for use in everyday life obtain significantly higher speech recognition scores (as a group) with the preferred strategy than with nonpreferred ones. DESIGN: The first 100 adults implanted with the Nucleus 24 Cochlear Implant System who had a minimum of 3 mo experience with the device were invited to participate. Those who accepted were randomly assigned to one of two groups for an initial 6-wk use of either the ACE or the CIS strategy; the other strategy was used during the second 6-wk period. Parameters in subjects' SPrint speech processor programs were adjusted to maximize perceived benefit with each strategy in everyday life. Recognition of medial consonants and vowels, CNC words, CUNY sentences in quiet and at + 10 dB signal to noise ratio, and HINT sentences in quiet was initially evaluated at the beginning of the study with the SPEAK strategy and at the end of the two 6-wk periods with the ACE and CIS strategies. Then subjects' processors were programmed with all three strategies for use in everyday life. After 3-wk use, a final evaluation of speech recognition with the HINT sentences in quiet and CUNY sentences at +10 dB signal to noise ratio was performed with each strategy. Subjects also responded to a questionnaire giving their strategy preference for most listening situations, the percentage of time they used each strategy, and the strategy they found gave them the best hearing and understanding of speech in 19 listening situations. RESULTS: Of the 62 subjects who participated, 56 subjects reported that they preferred one strategy for most listening situations (ACE strategy: 37 [59.7%]; SPEAK strategy: 14 [22.6%]; CIS strategy: 5 [8.0%]) and six subjects did not prefer a single strategy (9.7%). For the group who preferred one strategy, the preferred strategy resulted in higher scores than for one of the other strategies at the initial evaluation on CUNY sentences in quiet and noise and at the final evaluation on HINT sentences in quiet and CUNY sentences in noise for approximately two-thirds of the subjects. Strategy preference and performance were not significantly related for the remaining dependent measures. There also was strong agreement between the preferred strategy, percentage time this strategy was used, and the number of specific listening situations the preferred strategy was chosen for best hearing and understanding of speech. Although the majority of subjects strongly preferred a single strategy, some preferred to use two or three strategies, and a few were not sure which strategy they preferred for the majority of listening situations. Of the 19 subjects who reported that it was useful to use different strategies for different listening situations, only 5 of the 13 subjects, who responded to a follow-up questionnaire sent 18 mo later, continued to use multiple strategies. CONCLUSIONS: There was a significant relation between subjects' strategy preference based on experience in everyday life and their performance on the sentence tests, particularly sentences in noise. Important individual differences in strategy preference as well as in rate and number of channels stimulated per cycle within the ACE and CIS strategies emerged during the study. At the end of this process, over half of the subjects preferred the ACE strategy, and over double the number preferred the SPEAK strategy compared with the CIS strategy. To provide newly implanted recipients with as much benefit as possible, it is important that the speech processor program with each strategy be adjusted to maximize perceived benefit sequentially and then the three strategies need to be compared. With the four memories of the SPrint processor and a recipient who adapts quickly to hearing sound with different speech coding strategies, it may be possible to accomplish this comparison clinically through weekly fitting sessions plus listening in everyday life over a period of approximately 6 wk. At the end of this fitting process, most recipients probably will prefer to use one strategy, whereas some may prefer two or all three strategies to maximize their ability to hear in different listening situations.

The nucleus 24 contour cochlear implant system: adult clinical trial results.

OBJECTIVE: The purpose of this article is to present psychophysical data for 40 Nucleus 24 Contour adult patients with 1 mo of device experience and speech perception results for a group of 56 adult patients with 3 mo experience using the Nucleus 24 Contour cochlear implant system. Postoperative hearing thresholds (i.e., under headphones) in the implanted ear were also assessed in a group of 85 patients who had measurable hearing preoperatively. This was of interest because preservation of residual hearing, postoperatively, is consistent with atraumatic insertion of the electrode array. In addition, data will be presented that reflected feedback from 40 surgeons who participated in the trial. DESIGN: Participants in this study were 18 yr of age or older, with bilateral severe to profound sensorineural hearing loss with no congenital component. Preoperatively, they scored < or = 50% open-set sentence recognition (HINT sentences) in the ear to be implanted and < or = 60% in the best-aided condition. The investigation was a repeated-measures single-subject experiment and took place at 46 different North American clinical sites. Preoperative performance was compared with postoperative performance 3 mo after device activation. Clinicians were able to program patients' processors with one, two, or all three speech-processing strategies. Testing took place using the participant's preferred speech-processing strategy (SPEAK, CIS, or ACE). Preoperative unaided hearing thresholds were compared with unaided thresholds in the implanted ear measured 1 mo after device activation. Surgeons were canvassed regarding surgical use and design of the device via a questionnaire after having completed at least one Nucleus 24 Contour surgery. RESULTS: Average T- and C-levels for the Nucleus 24 Contour patients were considerably lower than those using the Nucleus 24 (CI24M). A total of 85 patients had measurable hearing preoperatively at two or more audiometric frequencies in the ear implanted. Of these patients 41 (48%) had measurable hearing at one or more frequencies and 32 (38%) had measurable hearing at two or more frequencies postoperatively. In general, surgeons found the Nucleus 24 Contour easy to insert and were pleased with the design features of the device. The downsized receiver/stimulator (of the Nucleus 24 Contour) required less drilling than the Nucleus 24, reducing surgical time, as well as making the Contour better suited for implantation in those with small skull sizes (e.g., small children and infants). After 3 mo of device use, mean open-set speech perception in quiet and in noise was significantly better than preoperative performance on all test measures. Patients using the ACE strategy had significantly better mean scores for all measures than patients using SPEAK. Only two patients preferred to use the CIS coding strategy. CONCLUSIONS The results presented in this article demonstrated that the design objectives of the Nucleus 24 Contour were met. Namely, results from this study, together with insertion studies, were consistent with perimodiolar placement using an implant design that the majority of surgeons found easy to insert with relatively minimal trauma. Reduced T- and C-levels were observed with Contour patients when compared with patients using the Nucleus 24 with the straight array, consistent with perimodiolar placement. A survey of surgeons participating in the clinical trial indicated easier, or equally easy, insertion of the Contour array, compared with previous Nucleus products as well as other manufacturers' devices, without the use of additional insertion tools or array positioners. Postoperatively, 46% of patients with preoperative residual hearing maintained some level of unaided hearing postoperatively, suggesting atraumatic insertion of the Nucleus 24 Contour electrode array. It is worth noting that all 216 patients implanted during this study had full insertions of their Contour electrode arrays. High levels of open-set speech perception in quiet and in noise were achieved and patients using the ACE strategy had significantly better mean scores for all measures than patients using SPEAK. Only two patients preferred to use the CIS coding strategy.