Effect of exceeding compliance voltage on speech perception in cochlear implants.

OBJECTIVES: In cochlear implants, the maximum current I (Amperes) that can be delivered on a cochlear implant electrode is determined by V = I * R, where V = compliance voltage (Volts) and R = electrode impedance (Ohms). Generally, electrode impedances are measured during each clinical visit and are used to set electrical stimulation parameters in cochlear implants. However, electrode impedances can rise during the course of cochlear implant use and lead to electrical stimulation voltage requirements exceeding the maximum compliance voltage of the medical device. Electric stimulation requirements that exceed the compliance voltage lead to clipping of the biphasic electrical pulse (current going into the cochlea) and are known to adversely affect cochlear implant outcomes. DESIGN: Thirteen (11 unilateral and 2 bilateral) Advanced Bionics cochlear implant patients with a HiRes 90k™ cochlear implant participated in this study. Speech perception scores were measured using the patient's baseline clinical program with the most comfortable loudness levels (M-levels) and the following four test programs: (1) stimulation clipped at 15% below clinical M-levels (15%C) (2) stimulation clipped at 30% below clinical M-levels (30%C) (3) M-levels decreased by 15% (15%M) and (4) M-levels decreased by 30% (30%C). Speech perception scores were measured using AzBio sentences presented at 60 dB SPL in quiet and in the presence of multi-talker babble (+10 dB SNR). RESULTS: Relative to the clinical baseline program, speech perception scores with the four test programs decreased in both quiet and noisy listening conditions. In quiet, speech perception scores measured with the 30%M and 30%C programs were significantly (p < 0.001) poorer than the baseline program. No significant differences in speech perception scores were measured between the baseline and the 15%C or 15%M programs. In the noisy listening condition, speech perception scores were significantly poorer than the baseline program for the 15%C (p = 0.008), 30%C (p < 0.001), and 30%M (p < 0.001) programs. No significant differences in speech perception scores were obtained between the baseline and the 15%M program in the noisy listening condition. Speech perception scores measured with the 30%C program were significantly (p < 0.001) poorer than those with the 30%M program, suggesting that clipping was more detrimental than reducing electrical stimulation levels. CONCLUSION: Small amounts (15%) of clipping can significantly decrease speech perception in the presence of background noise. Large amounts (30%) of both clipping and M-level reduction may lead to significantly poorer speech perception in quiet and in background noise. The decrease in speech perception scores can most likely be attributed to reduced volume and poorer spectro-temporal representation. Therefore, it is important to establish comfortably loud electrical stimulation levels without exceeding the compliance voltage to maximize cochlear implant outcomes.

Increase in cochlear implant electrode impedances with the use of electrical stimulation.

OBJECTIVE: Electrode impedances play a critical role in cochlear implant programming. It has been previously shown that impedances rise during periods of non-use, such as the post-operative recovery period. Then when the device is activated and use is initiated, impedances fall and are typically stable. In this study, we report a new pattern where electrode impedances increase with device use and decrease with device rest. DESIGN: Electrode impedances were measured three to four times every day over a span of 1-3 months for two cochlear implant patients. STUDY SAMPLE: Two patients with a Nucleus cochlear implant participated in this study. RESULTS: Both subjects in this study show wide fluctuations in electrode impedances. By taking serial electrode impedance measurements throughout a day of use, we observe that electrode impedances consistently increase with device use and decrease with device rest. CONCLUSION: In this study, we report two cases of electrode impedances increasing as a function of device use. Numerous management strategies were employed to reduce this effect but none prevailed; a clear pathophysiologic mechanism remains elusive. Further study into the cause of this electrode impedance pattern is warranted to establish a management strategy for these cochlear implant users.

Monitoring Cochlear Nerve Integrity During Vestibular Schwannoma Microsurgery in Real-Time Using Cochlear Implant Evoked Auditory Brainstem Response and Streaming Neural Response Imaging.

OBJECTIVE: Intraoperative far-field auditory brainstem response (ABR) and direct cochlear nerve action potential monitoring using neural response imaging (NRI) are techniques for monitoring the cochlear nerve during vestibular schwannoma (VS) surgery. A new paradigm has developed where the cochlear nerve is anatomically preserved during tumor removal to facilitate cochlear implantation in select circumstances. This report describes the use of an unmodified commercial cochlear implant (CI) to elicit electrically-evoked direct cochlear nerve and far-field ABR monitoring to evaluate the status of the cochlear nerve during tumor resection in real time. PATIENTS: Adult female with unilateral, sporadic VS. INTERVENTION(S): Cochlear implantation followed by translabyrinthine resection of VS in single operation. MAIN OUTCOME MEASURES: During tumor resection intra-cochlear electrodes were used to deliver electrical stimulation and measure NRI or the cochlear nerve action potential. Electrically-evoked ABR (eABR) was measured using surface electrodes and wave V was monitored (far-field ABR) during surgery. RESULTS: A 61-year-old female was evaluated for a unilateral, enlarging intracanalicular VS with asymmetric SNHL. The patient opted for microsurgery and due to her bilateral hearing loss was a candidate for CI. Cochlear implantation with an unmodified, commercially available lateral wall electrode was performed. The remainder of the approach and tumor resection was performed under continuous eABR and NRI monitoring. Gross total resection was achieved with intact eABR and NRI at the conclusion of the case. Changes in ABR and NRI consistently recovered after modifying dissection strategy. The patient reported auditory percepts with her cochlear implant postoperatively. CONCLUSIONS: This report demonstrates the feasibility of using real-time NRI and eABR with a CI to facilitate preservation of the cochlear nerve during VS microsurgery. Using this method to mitigate cochlear nerve trauma during microsurgery may preserve the option of CI for hearing rehabilitation.

Application of Kaizen Principles to a Large Cochlear Implant Practice: A Continuous Quality Improvement Initiative at Mayo Clinic.

OBJECTIVE: To remove barriers and improve access for patients seeking cochlear implantation. STUDY DESIGN: Prospective quality improvement study at a large tertiary academic care center. METHODS: A Kaizen quality improvement model was applied over the course of a year. Four weeklong meetings were used to identify areas for improvement and remediation. Data were collected at baseline, 90-days, and 1-year postcompletion of the project. Outcome measures included lead times, defined as the wait time between first contact with the clinic and the first appointment, and the wait time between surgery and activation, and cycle times defined as the total test time needed to determine cochlear implant candidacy, and total time needed to complete initial activation. The total inventory kept as clinic stock was also calculated RESULTS:: Kaizen team members collected data for each outcome measure. After the Kaizen principles were applied, the following outcomes were observed: median lead times between first contact with the clinic to candidacy testing, candidacy testing to surgery, and surgery to activation of the implant remained stable from baseline to 1-year follow-up. Median cycle time for candidacy testing decreased from 7.3 hours at baseline to 3.0 hours at 1-year follow-up. Cycle times for initial activation of the device did not change over time. The total inventory of clinic stock was reduced by 31%. CONCLUSIONS: Though outcomes for lead and cycle times varied, implementation of Kaizen principles was found to be an effective method for completing this quality improvement project at a large cochlear implant program overall. LEVEL OF EVIDENCE: 3a.

Cochlear Implantation in Charcot-Marie-Tooth Disease: Case Report and Review of the Literature.

INTRODUCTION: Charcot-Marie-Tooth (CMT) disease is a peripheral hereditary neuropathy associated with motor and sensory impairment and can result in profound sensorineural hearing loss (SNHL). Currently, the role of cochlear implantation in the setting of CMT and other progressive peripheral neurodegenerative disorders is not well established. METHODS: Case report and review of the English literature. RESULTS: A 70-year-old male with CMT was referred for evaluation of progressive asymmetric SNHL and reported a 15-year duration of deafness involving the left ear. Audiometric testing confirmed profound SNHL in the left ear, while the right ear exhibited moderate-to-severe SNHL. Left-sided cochlear implantation was performed using a conventional length lateral wall electrode. Intraoperative device testing found normal impedance levels throughout the array; however, electrically evoked auditory potentials were absent on all electrodes. Upon initial activation 3 weeks after surgery, the patient reported excellent access to sound in the cochlear implant-only condition. He has made good progress at each subsequent visit; speech perception testing after seven months showed improvement from 0% to 32% on AzBio sentence and 53% on CNC phoneme testing in the cochlear implant-only condition. CONCLUSION: We report the third case of cochlear implantation in a patient with CMT. SNHL in CMT is hypothesized to result from disruption of synchronous activity of the cochlear nerve. In patients with CMT, cochlear implantation may reconstitute synchronous neural activity by way of supraphysiological electrical stimulation. Our results corroborate two earlier reports that cochlear implantation is a viable option for rehabilitation of SNHL in this unique subset of patients.

Cochlear Implantation in Adults With Asymmetric Hearing Loss: Speech Recognition in Quiet and in Noise, and Health Related Quality of Life.

OBJECTIVE: To examine the possible speech recognition and health related quality of life (HRQoL) benefits of cochlear implantation among adults with asymmetric sensorineural hearing loss. STUDY DESIGN: Retrospective chart review, single-subject design. METHODS: A total of 45 adult cochlear implant recipients with asymmetric sensorineural hearing loss where performance for the best-aided condition exceeded 60% correct open set sentence recognition in quiet, and the implanted ear met traditional candidacy criteria. End point testing of the implanted ear was evaluated with use of the Consonant-Vowel Nucleus-Consonant (CNC) word test and AzBio sentence test materials in quiet, and bimodally with the AzBio sentence test materials in noise at +5 dB signal-to-noise ratio (SNR). HRQoL was measured using the Nijmegen Cochlear Implant Questionnaire (NCIQ). RESULTS: Measured in quiet, with the non-implanted ear plugged, the average CNC word scores increased from 9.1% preoperatively to 55.7% (p < 0.01) at the 6-month post-activation test interval. Similarly, average AzBio sentence scores in quiet, with the non-implanted ear plugged, increased from 13.9% preoperatively to 73.4% (p < 0.01) at the 6-month post-activation test interval. Finally, in the bilateral/bimodal condition, the AzBio sentence score in +5 dB SNR improved from an average of 26.8% preoperatively to 52.4% (p < 0.01) at the 6-month test interval. Results of the NCIQ showed improved scores on all six subdomains. CONCLUSIONS: These data demonstrate significant benefit of cochlear implantation among a group of postlingually deafened adults whose preoperative hearing and aided speech recognition fell outside of the currently specified Food and Drug Administration candidacy guidelines. Results of this study support the evaluation of a candidate's speech recognition in noise in the best-aided condition to adequately assess candidacy for a cochlear implant.

Early outcomes after cochlear implantation for adults and children with unilateral hearing loss.

OBJECTIVES/HYPOTHESIS: This study was designed to examine speech recognition and self-perceived health-related quality of life (HRQoL) received from cochlear implantation among a cohort of adults and children with a short duration of unilateral hearing loss greater than 6 months, but less than 2 years. STUDY DESIGN: Single-subject repeated measures prospective study. METHODS: This study assessed changes in speech recognition and self-perceived quality of life by prospectively analyzing data at the preoperative evaluation and at the 3-month and 6-month postactivation intervals. Measurement tools included Medical Outcomes Study Questionnaire Short Form 36, Nijmegen Cochlear Implant Questionnaire, Speech Spatial and Qualities of Hearing-Comparative, and speech recognition measures in quiet and in noise. RESULTS: Results indicated significant improvement in speech recognition, both in quiet and noise. Quality-of-life measures showed a significant increase in self-perceived benefit with disease-specific instruments, but remained constant with a generic HRQoL instrument. CONCLUSIONS: Cochlear implantation was a successful intervention for improved hearing in quiet and noise, and a self-perceived benefit for this group of adults and children with a short duration of unilateral hearing loss. LEVEL OF EVIDENCE: 4 Laryngoscope, 127:1683-1688, 2017.

Availability of binaural cues for bilateral implant recipients and bimodal listeners with and without preserved hearing in the implanted ear.

The purpose of this study was to examine the availability of binaural cues for adult, bilateral cochlear implant (CI) patients, bimodal patients and hearing preservation patients using a multiple-baseline, observational study design. Speech recognition was assessed using the Bamford-Kowal-Bench Speech-in-Noise (BKB-SIN) test as well as the AzBio sentences [Spahr AJ, et al: Ear Hear 2012;33:112-117] presented in a multi-talker babble at a +5 dB signal-to-noise ratio (SNR). Test conditions included speech at 0° with noise presented at 0° (S0N0), 90° (S0N90) and 270° (S0N270). Estimates of summation, head shadow (HS), squelch and spatial release from masking (SRM) were calculated. Though nonwwe of the subject groups consistently showed access to binaural cues, the hearing preservation patients exhibited a significant correlation between summation and squelch whereas the bilateral and bimodal participants did not. That is to say, the two effects associated with binaural hearing - summation and squelch - were positively correlated only for the listeners with bilateral acoustic hearing. This finding provides evidence for the supposition that implant recipients with bilateral acoustic hearing have access to binaural cues, which should, in theory, provide greater benefit in noisy listening environments. It is likely, however, that the chosen test environment negatively affected the outcomes. Specifically, the spatially separated noise conditions directed noise toward the microphone (mic) port of the behind-the-ear (BTE) hearing aid and implant processor. Thus, it is possible that in more realistic listening environments for which the diffuse noise is not directed toward the processor/hearing aid mic, hearing preservation patients have binaural cues for improved speech understanding.

Improving speech perception in noise for children with cochlear implants.

BACKGROUND: Current cochlear implant recipients are achieving increasingly higher levels of speech recognition; however, the presence of background noise continues to significantly degrade speech understanding for even the best performers. Newer generation Nucleus cochlear implant sound processors can be programmed with SmartSound strategies that have been shown to improve speech understanding in noise for adult cochlear implant recipients. The applicability of these strategies for use in children, however, is not fully understood nor widely accepted. PURPOSE: To assess speech perception for pediatric cochlear implant recipients in the presence of a realistic restaurant simulation generated by an eight-loudspeaker (R-SPACE™) array in order to determine whether Nucleus sound processor SmartSound strategies yield improved sentence recognition in noise for children who learn language through the implant. RESEARCH DESIGN: Single subject, repeated measures design. STUDY SAMPLE: Twenty-two experimental subjects with cochlear implants (mean age 11.1 yr) and 25 control subjects with normal hearing (mean age 9.6 yr) participated in this prospective study. INTERVENTION: Speech reception thresholds (SRT) in semidiffuse restaurant noise originating from an eight-loudspeaker array were assessed with the experimental subjects' everyday program incorporating Adaptive Dynamic Range Optimization (ADRO) as well as with the addition of Autosensitivity control (ASC). DATA COLLECTION AND ANALYSIS: Adaptive SRTs with the Hearing In Noise Test (HINT) sentences were obtained for all 22 experimental subjects, and performance-in percent correct-was assessed in a fixed +6 dB SNR (signal-to-noise ratio) for a six-subject subset. Statistical analysis using a repeated-measures analysis of variance (ANOVA) evaluated the effects of the SmartSound setting on the SRT in noise. RESULTS: The primary findings mirrored those reported previously with adult cochlear implant recipients in that the addition of ASC to ADRO significantly improved speech recognition in noise for pediatric cochlear implant recipients. The mean degree of improvement in the SRT with the addition of ASC to ADRO was 3.5 dB for a mean SRT of 10.9 dB SNR. Thus, despite the fact that these children have acquired auditory/oral speech and language through the use of their cochlear implant(s) equipped with ADRO, the addition of ASC significantly improved their ability to recognize speech in high levels of diffuse background noise. The mean SRT for the control subjects with normal hearing was 0.0 dB SNR. Given that the mean SRT for the experimental group was 10.9 dB SNR, despite the improvements in performance observed with the addition of ASC, cochlear implants still do not completely overcome the speech perception deficit encountered in noisy environments accompanying the diagnosis of severe-to-profound hearing loss. CONCLUSION: SmartSound strategies currently available in latest generation Nucleus cochlear implant sound processors are able to significantly improve speech understanding in a realistic, semidiffuse noise for pediatric cochlear implant recipients. Despite the reluctance of pediatric audiologists to utilize SmartSound settings for regular use, the results of the current study support the addition of ASC to ADRO for everyday listening environments to improve speech perception in a child's typical everyday program.

Cochlear implantation in the octogenarian and nonagenarian.

OBJECTIVE: Previous studies have shown that cochlear implant outcomes with respect to surgical morbidity and speech perception may be poorer in elderly patients as compared with younger adults. However, recent anecdotal reports suggest that elderly cochlear implant recipients are achieving increasingly higher speech perception performance and fewer surgical complications than previously noted. Our objective is to review cochlear implant outcomes using newer generation implants and minimally traumatic cochleostomy techniques in patients 80 years and older compared with younger adult recipients. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral center. PATIENTS: All adult cochlear implant recipients (232 patients, 258 implants) who underwent implantation with a Nucleus Freedom, Advanced Bionics HR90k, or Med El Sonata device at a tertiary academic institution. INTERVENTION(S): Postoperative speech perception scores and clinical data extraction using the electronic medical record. MAIN OUTCOME MEASURE(S): Anesthetic and surgical complications, device malfunction, operative time, admission status, length of hospital stay, and postoperative speech perception scores were collected after 50 cochlear implant procedures in patients who were implanted beyond the eighth decade and 208 among younger adults (18-79 yr). RESULTS: Patients 80 years or older were more likely to have anesthetic complications and require hospital admission (p < 0.05). There was no statistical difference between groups with respect to surgical complications or device malfunction. Speech perception analysis revealed similar outcomes for older and younger patients. CONCLUSION: Cochlear implantation is well tolerated across all adult age groups with a relatively low risk for adverse surgical events or device malfunction. Given the favorable safety profile and high levels of speech perception achieved by older patients, routine implantation of octogenarian and nonagenarians seems warranted. These results also stress the need for thorough preoperative evaluation of elderly patients, given the increased likelihood for perioperative anesthetic complications.