Evaluation of a Totally Implantable Cochlear Implant in Adults With Bilateral Sensorineural Hearing Loss: A Feasibility Study.

objectivesTo investigate the feasibility of a newly designed investigational totally implantable cochlear implant, the Cochlear ™ totally implantable cochlear implant (TICI) Research System, which enables hearing without the use of an external sound processor.

designA prospective, single-treatment arm, repeated measures feasibility study to investigate clinical benefit and safety. Ten adult participants with bilateral moderately severe-to-profound sensorineural hearing loss were implanted unilaterally with the TICI Research System. Co-primary endpoints evaluated external hearing (EH) mode (i.e., sound processor on) and invisible hearing (IH) mode (i.e., sound processor off) performance using words in quiet (60 dB SPL) and sentences in babble noise (60 dB SPL, +10 dB SNR) from the preoperative baseline to 6-month post-activation. The same speech perception tests were re-measured at 12-month post-activation. At 9-month post-activation, performance using phonemes in quiet was measured at a wider range of speech input levels (45, 55, 65, and 75 dB SPL), such as would be encountered in real-life settings. Patient-reported outcomes were evaluated using the Speech, Spatial, and Qualities of Hearing scale, Global Health Utilities Index mark 2/3, and Patient Satisfaction Survey. Device data logging captured time of use statistics in each hearing mode. Safety outcomes (adverse events and device deficiencies) were reported for the study duration (up to 2 years post-implantation).

resultsSpeech performance with the TICI Research System for both EH and IH modes at 6 months was significantly improved over baseline (n = 9). For words in quiet, there was a mean improvement of 38.5% (95% confidence interval [CI], 24.6 to 52.5) and 25.2% (95% CI, 13.7 to 36.7) for EH and IH, respectively. For sentences in noise, there was a mean improvement of 74.8% (95% CI, 53.4 to 96.2) and 64.5% (95% CI, 42.9 to 86.0) for EH and IH, respectively. For words in quiet, performance was found to be significantly better for EH compared with IH, with marginal mean differences of 13.3% ( p < 0.001) and 12.0% ( p = 0.004) at 6 and 12 months, respectively. Likewise, for phonemes in quiet at 9 months, EH was significantly better than IH with differences of 33.9% ( p < 0.001), 21.7% ( p < 0.001), and 9.8% ( p = 0.002) at 45, 55 and 65 dB SPL, respectively, with no significant difference at 75 dB SPL ( p = 0.384). For sentences in noise, at 6 months, EH had significantly better performance than IH with a marginal mean difference of 10.3% ( p = 0.021), with no difference shown at 12 months ( p = 1.000). Speech, Spatial, and Qualities of Hearing scale showed a significant mean improvement of 1.84 (95% CI, 1.00 to 2.65) compared with baseline. Health Utilities Index mark 2/3 showed variability in scores across the participant cohort, and Patient Satisfaction Survey ratings showed that overall, participants were satisfied with the device. Data logging showed participants' use of IH varied from 22% to 88% of total listening time (median 49%). Device failures occurred in 2 participants due to a microphone-related fluid ingress issue. Both participants were reimplanted with conventional Cochlear Nucleus ® devices. No other safety issues were detected.

conclusionsThis study demonstrated the feasibility of the TICI Research System to provide patient benefit in both IH and EH modes. No fundamental problem with the use of a transcutaneous microphone was detected. These findings support further development of the TICI design and approach.