Multichannel auditory brainstem implant: US clinical trial results.

Since 1994, a US Food and Drug Administration clinical trial evaluated the multichannel auditory brainstem implant (ABI) on 92 subjects with neurofibromatosis type 2 (NF2). The trial has shown that 85 per cent of patients receive auditory sensations. A small number of patients demonstrate a clinically significant degree of open-set sentence recognition in the sound-alone condition; however, when the ABI is combined with lip-reading cues, 93 per cent of patients demonstrate improved sentence understanding at three to six months. In addition, the majority of recipients report daily use of their devices, and satisfaction with the decision to receive the ABI.

Early results using the nucleus CI24M in children.

OBJECTIVE: To report early postimplantation speech recognition results in children who received Nucleus CI24M cochlear implants. STUDY DESIGN: The study group consisted of 19 consecutively implanted children. PATIENTS AND SETTING: Congenitally deaf children (20 months to 15 years old) were implanted with the Nucleus CI24M and followed-up at New York University Medical Center for a period of 3 to 12 months. MAIN OUTCOME MEASURES: Speech perception was evaluated preoperatively and postoperatively using the Early Speech Perception (ESP) test, the Glendonald Auditory Screening Procedure (GASP) word and sentence tests, Phonetically Balanced Kindergarten (PBK) monosyllabic word lists, Common Phrases test, the Multisyllabic and Lexical Neighborhood (MLNT, LNT) tests, and the Banford-Kowal-Bench (BKB) sentence test. RESULTS: One-way analyses of variance revealed significant improvement in open-set speech recognition in children able to perform measurement tasks. CONCLUSIONS: The Nucleus CI24M cochlear implant provides significant benefit to children after short-term use.

Summary of results using the nucleus CI24M implant to record the electrically evoked compound action potential.

OBJECTIVE: This study outlines a series of experiments using the neural response telemetry (NRT) system of the Nucleus CI24M cochlear implant to measure the electrically evoked compound action potential (EAP). The goal of this investigation was to develop a protocol that allows successful recording of the EAP in a majority of CI24M cochlear implant users. DESIGN: Twenty-six postlingually deafened adults participated in this study. A series of experiments were conducted that allowed us to examine how manipulation of stimulation and recording parameters may affect the morphology of the EAP recorded using the Nucleus NRT system. RESULTS: Results of this study show consistent responses on at least some electrodes from all subjects. Cross-subject and cross electrode variations in both the growth of the response and the temporal refractory properties of the response were observed. The range of stimulus and recording parameters that can be used to record the EAP with the Nucleus NRT system is described. CONCLUSIONS: Using the protocol outlined in this study, it is possible to reliably record EAP responses from most subjects and for most electrodes in Nucleus CI24M cochlear implant users. These responses are robust and recording these responses does not require that the subject sleep or remain still. Based on these results, a specific protocol is proposed for measurement of the EAP using the NRT system of the CI24M cochlear implant. Potential clinical implications of these results are discussed.

The multichannel auditory brain stem implant: performance in twenty patients.

The auditory brain stem implant has been used effectively to provide hearing sensations to individuals deafened by bilateral auditory nerve tumors (neurofibromatosis type 2). During tumor removal, the auditory brain stem implant is implanted into the lateral recess of the fourth ventricle by a translabyrinthine approach and is intended to stimulate auditory neurons of the cochlear nucleus complex. A new eight-electrode multichannel auditory brain stem implant was developed and evaluated in 20 patients who had at least 3 months' experience with the device. Mild nonauditory sensations (primarily tingling in the head or torso) were encountered in some instances but could be managed by changing the stimulus characteristics or excluding electrodes. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores in three patients ranging from 49% to 58% and ability to converse on the telephone. These results indicate that significant auditory benefit can be derived from direct multichannel electrical stimulation of the auditory portion of the human brain stem.

Speech perception abilities of adult and pediatric Nucleus implant recipients using the Spectral Peak (SPEAK) coding strategy.

A series of 73 postlinguistically deafened adults and 34 prelinguistically deafened children were evaluated with the Spectral Peak (SPEAK) coding strategy of the Nucleus 22-channel cochlear implant. The adults who received consecutive implants demonstrated rapid acquisition of open-set speech recognition skills in the initial postoperative period. Group mean sentence recognition improved to 53.5% (n = 52) after 2 weeks, 62.1% (n = 55) after 1 month, 69.8% (n = 57) after 3 months, and 74.4% (n = 42) after 6 months of use. At the 6-month evaluation interval, 43% of subjects scored greater than 90% on sound-alone sentence recognition in quiet and only one patient (2.4%) scored less than 10%. Mean monosyllabic word recognition was 35.6% after 6 months of use. The 34 prelinguistically deafened children were converted from the Multipeak strategy to Spectral Peak strategy at four large pediatric implant centers. After 6 months of using the new coding strategy, the children demonstrated significant improvements in their speech perception abilities.

Factors affecting auditory performance of postlinguistically deaf adults using cochlear implants.

A model of auditory performance and a model of ganglion cell survival in postlinguistically deafened adult cochlear implant users are suggested to describe the effects of aetiology, duration of deafness, age at implantation, age at onset of deafness, and duration of implant use. The models were compared with published data and a composite data set including 808 implant users. Qualitative agreement with the model of auditory performance was found. Duration of deafness had a strong negative effect on performance. Age at implantation had a slight negative effect on performance, increasing after age 60 years. Age at onset of deafness had little effect on performance up to age 60. Duration of implant use had a positive effect on performance. Aetiology had a relatively weak effect on performance.

Evaluation of the Nucleus Spectra 22 processor and new speech processing strategy (SPEAK) in postlinguistically deafened adults.

A new speech processing strategy (SPEAK) has been compared with the previous Multipeak (MPEAK) strategy in a study with 24 postlinguistically deafened adults. The results show that performance with the SPEAK coding strategy was significantly better for 58.31% of subjects on closed-set consonant identification, for 33.3% of subjects on closed-set vowel identification and open-set monosyllabic word recognition, and for 81.8% of subjects on open-set sentence recognition in quiet and in competing noise (+ 10 dB signal-to-noise ratio). By far the largest improvement observed was for sentence recognition in noise, with the mean score across subjects for the SPEAK strategy twice that obtained with MPEAK.

Multichannel auditory brain stem implant: case studies comparing fitting strategies and results.

A new 8-electrode prosthesis has been developed for individuals deafened by bilateral auditory nerve tumors (neurofibromatosis-2). Twelve patients have received the multichannel auditory brain stem implant at House Ear Institute since 1992, 11 of whom receive useful auditory sensations. Processor fitting includes scaling and ranking of electrode-specific pitch sensations, and determination of any nonauditory sensations. Two representative patients differing in experience and number of usable electrodes are compared in terms of range of auditory sensations and speech perception performance. An inexperienced patient with two electrodes using a new speech-processing strategy (Speak) performed comparably to an experienced patient with six electrodes using an earlier feature-extraction processor.

Evaluation of a new spectral peak coding strategy for the Nucleus 22 Channel Cochlear Implant System.

Sixty-three postlinguistically deaf adults from four English-speaking countries participated in a 17-week field study of performance with a new speech coding strategy, Spectral Peak (SPEAK), and the most widely used strategy, Multipeak (MPEAK), both of which are implemented on wearable speech processors of the Nucleus 22 Channel Cochlear Implant System; MPEAK is a feature-extraction strategy, whereas SPEAK is a filterbank strategy. Subjects' performance was evaluated with an experimental design in which use of each strategy was reversed and replicated (ABAB). Average scores for speech tests presented sound-only at 70 dB SPL were higher with the SPEAK strategy than with the MPEAK strategy. For tests in quiet, mean scores for medial vowels were 74.8 percent versus 70.1 percent; for medial consonants, 68.6 percent versus 56.6 percent; for monosyllabic words, 33.8 percent versus 24.6 percent; and for sentences, 77.5 percent versus 67.4 percent. For tests in noise, mean scores for Four-Choice Spondees at +10 and +5 dB signal-to-noise ratio (S/N) were 88.5 percent versus 73.6 percent and 80.1 percent versus 62.3 percent, respectively; and for sentences at +15 dB, +10, and +5 dB S/N, 66.5 percent versus 43.4 percent, 61.5 percent versus 37.1 percent, and 60.4 percent versus 31.7 percent, respectively. Subjects showed marked improvement in recognition of sentences in noise with the new SPEAK filterbank strategy. These results agree closely with subjects' responses to a questionnaire on which approximately 80 percent reported they heard best with the SPEAK strategy for everyday listening situations.

Scope and design of the clinical trial of the Nucleus multichannel cochlear implant in children.

Although much has been learned in the 5 yr since the first child received a multichannel cochlear implant, we remain at the very early stages of this endeavor. The current evaluation procedures and performance data detailed in subsequent chapters represent the continuation of the efforts described above.

Consonant production in children receiving a multichannel cochlear implant.

Consonant production was investigated in 29 children participating in the federal Food and Drug Administration's clinical trials of the Nucleus WSP-III cochlear implant. Speech samples were collected preimplant and 1 year postimplant. A significantly greater number of children produced stop, nasal, fricative, and glide consonants postimplant. Voiced stop consonants were used by more children than the voiceless cognates; however, voiceless fricatives were used more than voiced fricatives. Visible places of articulation were used more frequently than less visible places of articulation. Comparisons to Smith's data (J Speech Hear Res 1975;18:795-811) revealed qualitative similarities but postimplant, quantitative differences were observed. Post hoc analyses of the data revealed some sounds were influenced more by an implant than other sounds and suggest the role of an implant upon spontaneous speech is complex.

Pediatric performance with the Nucleus 22-channel cochlear implant system.

Results from 80 pediatric subjects with 12 months of experience wearing the Nucleus multichannel cochlear implant are presented. The data suggest that children demonstrate statistically and clinically significant benefit across a broad spectrum of abilities with the implant. Significant postoperative improvement was demonstrated by 66 percent (51 of 77), 63 percent (45 of 72), and 46 percent (27 of 59) of subjects tested on suprasegmental (prosodic), closed-set and open-set tests, respectively. Forty-nine percent of subjects tested improved when lipreading was combined with sound from the implant, compared with lipreading alone. Children who were deaf at an early age or who had longer duration deafness tended to demonstrate poorer performance on the more difficult perceptual tasks after 12 months of implant experience. However, preliminary evidence suggests that continued improvements by congenital and prelinguistic subjects over longer periods of time may reduce performance differences between subjects with early and later onset deafness.

Speech production performance in children with multichannel cochlear implants.

The purpose of this study is to report on five speech production protocols collected as part of the Food and Drug Administration's Clinical Trials for the Nucleus multichannel cochlear implant. Sixty-one children, ranging in age from 2.4 years to 17.8 years, participated. Speech measures included nonsegmental and segmental portions of the Phonetic Level Speech Evaluation, the Phonologic Level Speech Evaluation, speech intelligibility, and an experimental condition examining speech produced with the device turned on versus off. Seventy-seven percent of the children improved on at least one-third of the speech production measures. Significant improvements in the ability to imitate prosodic characteristics were observed for 31.1 percent of the children. Improvements in the ability to imitate speech sounds were found for 66.7 percent of the children. Examination of phonologic skills acquired during spontaneous speaking improved for 55.6 percent of the children. Speech intelligibility improved in 62.9 percent of the children after implantation. More centralized second formant frequencies were observed in vowels produced with the speech processor turned off, as opposed to on, in all 13 of the children tested on this protocol. Data from this study suggest a multichannel cochlear implant may assist many children in developing better speech.

Perceptual and production abilities in profoundly deaf children with multichannel cochlear implants.

A total of 218 children have been implanted to date with the Nucleus multichannel cochlear implant. All children have stimulated and there have been only 6 complications that required subsequent surgical intervention. After 12 months of experience with the device, significant improvements in auditory-alone speech perception were demonstrated by 66 percent of subjects tested on prosodic and closed-set measures and by 46 percent of subjects tested for open-set word recognition.

Clinical evaluation of a new ECoG recording electrode.

Noninvasive, extratympanic electrocochleography (ECoG) was performed on 13 normal-hearing subjects with three different types of ECoG electrodes. Two of these electrodes, the Life-Tech and Axonics-3M designs are commercially available, and widely used clinically. The third electrode, the TM electrode, is a newly designed system intended to be placed directly onto the tympanic membrane. The purpose of this study was to assess the clinical performance of these different electrodes with particular attention to response amplitudes, response variability, and practical ease of use. The results indicate that the TM electrode provides improved ECoG response amplitudes while minimizing clinical preparation time.