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Objective: The purpose of this study was to investigate the operating characteristics of the Nucleus 20 + 2L lateral wall cochlear implant including speech recognition results., Study Design: This was a prospective randomized study involving five different modes of stimulation., Setting: This study was carried out in an academic, tertiary referral center., Patients: The patients included in this study were adult cochlear implant candidates ages 44-74 years. Length of deafness ranged from 1 to 58 years with a variety of etiologies., Interventions: All patients were implanted with a 20 + 2L implant, which includes an intrascalar electrode array and an apically placed extracochlear, titanium encased ball electrode in contact with the endosteum of the apical turn. All patients underwent psychophysical and speech recognition testing in five different modes of electrode configuration., Main Outcome Measure(s): The main outcome measures included thresholds, comfort levels, dynamic ranges, and speech recognition results obtained in five electrode configuration modes., Results: Thresholds were significantly lower (repeated measures ANOVA) in both monopolar conditions when compared to bipolar mode of stimulation. A binomial statistical analysis indicated that in five of nine patients activated in all five modes of stimulation, the monopolar modes of stimulation resulted in improved speech recognition scores., Conclusions: The results of the study demonstrate the feasibility of the use of an apical lateral cochlear wall electrode in conjunction with an intrascalar electrode array. It further demonstrated the superiority of monopolar stimulation in selected patients. more...

Objective: To summarize the current applications of auditory evoked potential in children with cochlear implants and candidates for implantation., Patients and Methods: Perioperative transtympanic EABR is used routinely for ear selection and to establish the electrical stimulability of the ear intended to be implanted. The perioperative transtympanic EABR is supplemented with EABR obtained immediately following the insertion of the electrode array and the seating of the implant's receiver. Postoperatively, EABR and averaged electrode voltages are used effectively to properly adjust the implant stimulus parameters and to determine whether the implant is functioning adequately. Postoperatively, cognitive evoked potentials to speech and tonal stimuli may also be obtained., Results: EABR results have contributed to effective implant placement and function. There were several significant correlations between speech recognition and cognitive evoked potential., Conclusion: These measures help assure proper implant function and effective stimulus delivery. more...

A within-subjects comparison of monopolar versus bipolar stimulation was performed using a modified version of the Nucleus mini-22 cochlear implant, the Nucleus "20 + 2" implant. Six subjects underwent implantation with this device, which is identical to the Nucleus 22 cochlear implant with the addition of two extracochlear indifferent electrodes. These electrodes provide two monopolar modes of stimulation in addition to the standard bipolar modes used with the Nucleus 22 device. One of the indifferent electrodes is a ball placed under the temporalis muscle (MP1), whereas the second electrode is mounted on the lateral aspect of the receiver-stimulator (MP2). After a pre-experimental phase, subjects used each of three stimulation modes (BP + 1, MP1, and MP2) for a total of 4 weeks each. Variables tested with each mode included electric thresholds, comfort levels, dynamic ranges, and speech recognition. Both the MP1 and MP2 modes of stimulation required significantly less current than the bipolar mode (BP + 1) to reach threshold and comfort level. Analysis of dynamic range data also indicated a significant stimulation mode effect. However, stimulation in the various modes did not significantly affect speech recognition scores, although two subjects demonstrated significantly improved speech recognition scores when programmed in a monopolar mode. more...

Complete, irreversible failure of the implanted receiver-stimulator of the Cochlear Corporation multichannel implant are relatively rare. However, as the implanted patient population grows, malfunctions may be expected. From the over 200 patients implanted at the University of Michigan Medical Center, 6 patients with a complete and irreversible cochlear implant receiver-stimulator failure have been identified and treated. This represents a 3% failure rate. The amount of time between initial implantation and device failure ranged from 6 months to 3.5 years. Determination of device failure was made using psychophysical, electrophysiologic, and averaged electrode voltage measurements. The measurement of the average electrode voltages proved to be useful in determining the condition of the implant. Physiologic changes causing reduced electrical excitability were ruled out using psychophysical or electrophysiologic promontory testing. All patients were successfully explanted and reimplanted. more...

Numerous reports indicate that the cochlea remains responsive to electrical stimulation following labyrinthectomy. We report a case of a 47-year-old woman with a severe to profound sensorineural hearing loss from birth, who developed episodic vertigo with symptoms suggestive of delayed onset endolymphatic hydrops. Following 8 months of failed medical and vestibular rehabilitation management, a right-sided labyrinthectomy combined with cochlear implantation was performed without complication. Postoperatively the patient was free of vertigo. Attempts to activate the patient's device between 4 to 12 weeks after surgery were unsuccessful as stimulation of the electrodes resulted in discomfort. However, all 20 electrodes elicited comfortable hearing sensations 16 weeks postsurgery. One year after the successful activation, the patient demonstrated improved sound awareness and speech recognition with the implant when compared with preoperative performance with a hearing aid. This case study suggests that electrical detection thresholds with prosthetic stimulation may be unstable in the recently labyrinthectomized ear but supports and extends prior observations of preserved cochlear responsiveness after labyrinthectomy. more...

The effects of active channel number and place of stimulation on auditory-only performance with the Cochlear Corporation multichannel cochlear implant were investigated in seven subjects. A balanced crossover design was employed; subjects were initially programmed with either 10 basal or the full complement of 20 to 21 active electrodes. Following a 6-month period with the initial coding strategy, subjects were programmed with the alternate configuration, which they used for an additional 6 months. Auditory-only performance on suprasegmental, phoneme (vowel and consonant) open- and closed-set speech recognition was compared between the two electrode configurations. Additionally, performance with the first configuration and performance with the second configuration 3 days following programming were also compared. While a trend for increased scores was noted with 20 electrodes, especially with open-set speech recognition tasks, none of the differences between the two configurations reached statistical significance, as indicated by a Wilcoxon test. A comparison of performance at the end of the first 6-month period and 3 days following programming with the second configuration revealed a trend for reduced scores, especially on vowel tests. Overall, our results indicate that the feature extraction coding strategy associated with the Cochlear Corporation device allows patients to function well with only 10 basal electrodes and that speech recognition is only mildly affected initially when patients are programmed with a different encoding strategy. more...