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

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.

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.

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.