United States multicenter clinical trial of the cochlear nucleus hybrid implant system

Objectives/Hypothesis

To evaluate the safety and efficacy of acoustic and electric sound processing for individuals with significant residual low‐frequency hearing and severe‐to‐profound high‐frequency sensorineural hearing loss.

Study Design

Prospective, single‐arm repeated measures, single‐subject design.

Methods

Fifty individuals, ≥ 18 years old, with low‐frequency hearing and severe high‐frequency loss were implanted with the Cochlear Nucleus Hybrid L24 implant at 10 investigational sites. Preoperatively, subjects demonstrated consonant‐nucleus‐consonant word scores of 10% through 60% in the ear to be implanted. Subjects were assessed prospectively, preoperatively, and postoperatively on coprimary endpoints of consonant‐nucleus‐consonant words, AzBio sentences in noise, and self‐assessment measures.

Results

Significant mean improvements were observed for coprimary endpoints: consonant‐nucleus‐consonant words (35.8 percentage points) and AzBio sentences in noise (32.0 percentage points), both at P < 0.001. Ninety‐six percent of subjects performed equal or better on speech in quiet and 90% in noise. Eighty‐two percent of subjects showed improved performance on speech in quiet and 74% in noise. Self‐assessments were positive, corroborating speech perception results.

Conclusion

The Nucleus Hybrid System provides significant improvements in speech intelligibility in quiet and noise for individuals with severe high‐frequency loss and some low‐frequency hearing. This device expands indications to hearing‐impaired individuals who perform poorly with amplification due to bilateral high‐frequency hearing loss and who previously were not implant candidates.

Level of Evidence

2b. Laryngoscope, 126:175–181, 2016

Long-term outcomes of cochlear implantation in patients with high-frequency hearing loss

OBJECTIVE

To demonstrate the long-term benefits of implantation in patients with high-frequency sensorineural hearing loss, this report provides 5-year follow-up on a group of implant recipients who were subjects of the Cochlear™ Nucleus^® Hybrid™ L24 Implant System pivotal clinical study.

METHODS

The results of three related clinical studies were compiled to provide outcome data after 1, 3, and 5 years of implant use in a group of subjects who presented with preoperative high-frequency hearing loss and were implanted with a Nucleus Hybrid L24 (Cochlear Ltd., Sydney, Australia) cochlear implant. A subset of the 50 adult subjects (N = 32) who participated in the Hybrid L24 pivotal Investigational Device Exemption (IDE) completed comprehensive evaluations at 12 months postactivation, 3 years postactivation, and then as part of a postapproval study at 5 years postactivation. Testing included audiometric, speech perception, and subjective satisfaction measures.

RESULTS

Mean unilateral speech perception performance was significantly improved at all postoperative intervals compared to preoperative best-aided results and has remained stable to 5 years postactivation. Ninety-four percent of subjects had measurable hearing, and 72% continued to use electric-acoustic stimulation in the implanted ear after 5 years of implant use. Subjective satisfaction results support objective performance improvements.

CONCLUSION

Results demonstrate long-term success of patients with high-frequency hearing loss following Hybrid L24 (Cochlear) cochlear implantation. Benefits include speech perception abilities significantly better than those in the preoperative best-aided condition, with additional benefit in those using electric-acoustic stimulation in the implanted ear.

LEVEL OF EVIDENCE

2b. Laryngoscope, 1939-1945, 2018.

Using Neural Response Telemetry to Monitor Physiological Responses to Acoustic Stimulation in Hybrid Cochlear Implant Users

OBJECTIVE

This report describes the results of a series of experiments where we use the neural response telemetry (NRT) system of the Nucleus cochlear implant (CI) to measure the response of the peripheral auditory system to acoustic stimulation in Nucleus Hybrid CI users. The objectives of this study were to determine whether they could separate responses from hair cells and neurons and to evaluate the stability of these measures over time.

DESIGN

Forty-four CI users participated. They all had residual acoustic hearing and used a Nucleus Hybrid S8, S12, or L24 CI or the standard lateral wall CI422 implant. The NRT system of the CI was used to trigger an acoustic stimulus (500-Hz tone burst or click), which was presented at a low stimulation rate (10, 15, or 50 per second) to the implanted ear via an insert earphone and to record the cochlear microphonic, the auditory nerve neurophonic and the compound action potential (CAP) from an apical intracochlear electrode. To record acoustically evoked responses, a longer time window than is available with the commercial NRT software is required. This limitation was circumvented by making multiple recordings for each stimulus using different time delays between the onset of stimulation and the onset of averaging. These recordings were then concatenated off-line. Matched recordings elicited using positive and negative polarity stimuli were added off-line to emphasize neural potentials (SUM) and subtracted off-line to emphasize potentials primarily generated by cochlear hair cells (DIF). These assumptions regarding the origin of the SUM and DIF components were tested by comparing the magnitude of these derived responses recorded using various stimulation rates. Magnitudes of the SUM and DIF components were compared with each other and with behavioral thresholds.

RESULTS

SUM and DIF components were identified for most subjects, consistent with both hair cell and neural responses to acoustic stimulation. For a subset of the study participants, the DIF components grew as stimulus level was increased, but little or no SUM components were identified. Latency of the CAPs in response to click stimuli was long relative to reports in the literature of recordings obtained using extracochlear electrodes. This difference in response latency and general morphology of the CAPs recorded was likely due to differences across subjects in hearing loss configuration. The use of high stimulation rates tended to decrease SUM and CAP components more than DIF components. We suggest this effect reflects neural adaptation. In some individuals, repeated measures were made over intervals as long as 9 months. Changes over time in DIF, SUM, and CAP thresholds mirrored changes in audiometric threshold for the subjects who experienced loss of acoustic hearing in the implanted ear.

CONCLUSIONS

The Nucleus NRT software can be used to record peripheral responses to acoustic stimulation at threshold and suprathreshold levels, providing a window into the status of the auditory hair cells and the primary afferent nerve fibers. These acoustically evoked responses are sensitive to changes in hearing status and consequently could be useful in characterizing the specific pathophysiology of the hearing loss experienced by this population of CI users.

Intracochlear Recordings of Acoustically and Electrically Evoked Potentials in Nucleus Hybrid L24 Cochlear Implant Users and Their Relationship to Speech Perception

The Hybrid cochlear implant (CI) has been developed for individuals with high frequency hearing loss who retain good low frequency hearing. Outcomes have been encouraging but individual variability is high; the health of the cochlea and the auditory nerve may be important factors driving outcomes. Electrically evoked compound action potentials (ECAPs) reflect the response of the auditory nerve to electrical stimulation while electrocochleography (ECochG) reflects the response of the cochlear hair cells and auditory nerve to acoustic stimulation. In this study both ECAPs and ECochG responses were recorded from Nucleus Hybrid L24 CI users. Correlations between these two measures of peripheral auditory function and speech perception are reported. This retrospective study includes data from 25 L24 CI users. ECAPs and ECochG responses were recorded from an intracochlear electrode using stimuli presented at or near maximum acceptable loudness levels. Speech perception was assessed using Consonant-Nucleus-Consonant (CNC) word lists presented in quiet and AzBio sentences presented at a +5 dB signal-to-noise ratio in both the combined acoustic and electric (A+E) and electric (E) alone listening modes. Acoustic gain was calculated by subtracting these two scores. Correlations between these physiologic and speech perception measures were then computed. ECAP amplitudes recorded from the most apical electrode were significantly correlated with CNC scores measured in the E alone (r = 0.56) and A+E conditions (r = 0.64), but not with performance on the AzBio test. ECochG responses recorded using the most apical electrode in the intracochlear array but evoked using a 500 Hz tone burst were not correlated with either the scores on the CNC or AzBio tests. However, ECochG amplitude was correlated with a composite metric relating the additional benefit of acoustic gain in noise relative to quiet conditions (r = 0.67). Both measures can be recorded from Hybrid L24 CI users and both ECAP and ECochG measures may result in more complete characterization of speech perception outcomes than either measure alone.

The natural progression of low-frequency hearing loss in patients who meet hybrid implant system candidacy criteria

OBJECTIVES/HYPOTHESIS

To investigate the natural progression of hearing loss in patients with high-frequency hearing loss whose audiograms met the criteria for a hybrid cochlear implant (CI).

STUDY DESIGN

Retrospective database review.

METHODS

We retrospectively identified patients who met the criteria for a hybrid CI from our audiometric database. We also recorded the etiology of hearing loss in each patient and excluded patients with retrocochlear etiologies, those age <6 years, duration of observation <1 year, or those with a mixed or conductive hearing loss. We calculated the pre-CI progression of residual low-frequency (LF) hearing level in decibels per year and investigated the risk factor of the progression of hearing loss.

RESULTS

A total of 1,083 ears of 944 patients were included in this study. The average rate of hearing loss progression for all etiologies was 1.70 ± 0.10 dB/yr at an average of 250 Hz, 500 Hz, and 1 kHz in the affected ear(s). The progression of hearing loss was 5.0 ± 0.93 dB/yr in patients with Meniere's disease and 3.5 ± 0.76 dB/yr in those with autoimmune disease, both of which were significantly faster than progression rates in other etiologies. In patients with idiopathic, genetic/hereditary, and congenital hearing loss, the progression of hearing loss was 1.46 ± 0.10 dB/yr. Patients with steeply sloping hearing loss experienced significantly faster progression in the ipsilateral ear compared to patients with another audiometric type.

CONCLUSIONS

It is suggested that Meniere's disease, autoimmune-mediated inner ear disease, and steeply sloping hearing loss in the ipsilateral ear are risk factors for faster progression of residual LF hearing level.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1299-1303, 2020.