Normative findings of electrically evoked compound action potential measurements using the neural response telemetry of the Nucleus CI24M cochlear implant system.

One hundred and forty-seven adult recipients of the Nucleus 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15-30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles ('shift') and their slopes across the electrode array ('tilt'). Correlation between these two factors and the same factors describing the T- and C-levels appeared to be moderate, in the range of 0.5-0.6.

[Pediatric cochlear implants]. / Les implants cochléaires pédiatriques.

Indications for cochlear implants have been widened since 1995. Most implant candidates are children with severe congenital deafness. The cochlear implant must be inserted as early as possible for these children in order to optimize development of perception and language. A cochlear implant can also be discussed in certain particular cases for children with associated diseases, malformation of the inner ear, or severe deafness. The educational project must be realistic and take into account the future difficulties as well as an established set of criteria for successful language acquisition.

[The test for the evaluation speech perception and production]. / Test d'évaluation des perceptions et productions de la parole.

The aim of this paper is to present a Test to evaluate the speech perception and production in french profoundly hearing impaired children fitted with cochlear implant or traditional hearing aids. This test materials have been developed for children from 2 to 10 years old. This test fall into two basic categories known as speech perception and speech production. The assessment of the perceptual abilities through the use of the TEPPP is achieved across the hierarchy of perception which spans: detection, discrimination, identification, comprehension. The assessment of the speech production makes it possible to observe the speech production changes across three levels: phonetical, linguistical, intelligibility. The TEPPP, Test of Speech Perception and Production evaluation, enable us to observe if children, who receive a cochlear implant or a conventional hearing aids, obtain some degree of benefit in both speech perception and speech production.

Influence of communication mode on speech intelligibility and syntactic structure of sentences in profoundly hearing impaired French children implanted between 5 and 9 years of age.

OBJECTIVE: The purpose of this study was to examine the speech production in French profoundly hearing impaired children, focusing on word intelligibility, sentences syntax, and sentence pattern stages, by incorporating direct comparisons between speech production skills and communication modes in the same children. DESIGN: The design of the study incorporated a within-subject, repeated measures design for assessing speech production intelligibility and syntax. SETTING: Montpellier Pediatric Cochlear Implant Center. SUBJECTS: Twelve prelingually deafened French children who received a Nucleus multichannel cochlear implant (mean age at the time of implantation was 7 years 2 months) served as subjects for the speech production assessment. MAIN OUTCOME MEASURES: Speech production intelligibility, syntax, and sentence pattern stages were assessed at 1, 2 and 3 years postimplant. Speech production skills were related to the communication mode of the children (auditory-oral, four children; cued-speech, four children; sign-language, four children). RESULTS: Scores on word intelligibility steadily improved with increased experience with the implant, ranging from 18% before implantation to 54.5% at 36 months postimplantation in the overall population. The highest scores were found in the cued-speech group with an averaged score of 66.8% at 36 months postimplant. The number of syntactic elements increased over time with implant experience. Children receiving cued-speech education had higher scores by 3 years postimplantation than children receiving either auditory-oral or sign-language modes of communication. Language level (sentence pattern stages) also improved with increased experience with the device. By 3 years postimplantation, children receiving auditory-oral or cued-speech instruction were able to produce sentences; however, the sign-language children failed to do so at a rate comparable to the other children. Language level was significantly higher in the oralist or cued-speech educated children than in the sign-language group. CONCLUSIONS: Speech production skills improved with increased experience using a cochlear implant. Word intelligibility, syntactic structure of sentences, sentence pattern stages improved gradually over time. Production skills were greater in the cued-speech educated children group than in the auditory oral or sign-language groups. Statistically better sentence pattern stages were found in the auditory oral and sign-language groups.

Speech-perception performance in prelingually deafened French children using the nucleus multichannel cochlear implant.

PURPOSE: The speech-perception abilities of 36 French children, whose onset of deafness occurred before 2 years of age, was longitudinally examined after they received a Nucleus multichannel cochlear implant. METHODS: Speech perception was assessed in four areas: phoneme detection, closed-set word and sentence recognition; and modified open-set recognition. RESULTS: All children achieved phoneme detection by 3 months after implantation. Closed-set word and sentence recognition appeared initially less accurate in children with congenital deafness than in the prelingually deafened children; however, these differences disappeared by 18 months after implantation. Some modified open-set recognition was evident by 12 months after implantation and continued to improve 3 years after implantation. CONCLUSIONS: Data demonstrate significant improvements in speech perception with implant experience: 15 (60%) of 25 of the children identified sentences in closed sets, 22 (88%) of 25 identified words in closed sets after 12 months' experience, and 13 (81%) of 16 demonstrated open-set recognition after 24 months of implant use.

Functional maturation of the medial efferent olivocochlear system in human neonates.

The effect of contralateral acoustic stimulation on transient evoked otoacoustic emissions (TEOAE) was used to investigate the functional maturity of the medial efferent olivocochlear system in full term neonates and a 6-week-old baby. The technique used was to record the TEOAE alternately with and without contralateral noise. The result was a reduction in TEOAE amplitude and latency. This was best illustrated with a difference waveform obtained from the subtraction of the TEOAE waveform recorded with contralateral noise, from the waveform recorded without contralateral noise. All the full term neonates and also the 6-week-old baby showed significant effects indicating functional maturity of the medial olivocochlear system.

Evoked otoacoustic emissions from normal newborns and babies admitted to an intensive care baby unit.

Click-evoked otoacoustic emissions (OAEs) were recorded from both ears in two groups of neonates ranging in age from a few days to two months after birth. The first group consisted of 55 full-term neonates with normal developmental history and health status, including absence of middle ear disease and familial history of hearing loss. The second group consisted of 40 infants admitted to an intensive care baby unit for various pathological conditions (anoxia, prematurity, hyperbilirubinemia, meningitis). The method achieved 97% success in assessing cochlear function in the normal group; it was possible to identify a clear and reproducible response in all ears, except 3, at 70 dB SPL (i.e. approximately 30 dB nHL). The detection-threshold of OAEs was comparable to that measured in adult ears. Several babies from the second group produced no OAEs and were also tested by auditory brainstem responses (ABR): these infants demonstrated ABR thresholds higher than 30 dB nHL. OAEs provide an objective tool for a rapid and effective screening test for cochlear impairment in neonates.

A correlative study of evoked otoacoustic emission properties and audiometric thresholds.

Correlations were made between the detection thresholds of evoked otoacoustic emissions (EOAEs), subjective click thresholds, and mean audiometric thresholds in 240 normal and hearing-impaired ears. EOAEs have never been observed when subjective click thresholds or mean audiometric thresholds were equal to or greater than 35 dB HL. EOAEs were always found when click thresholds were equal to or lower than 15 dB HL and when mean audiometric thresholds were equal to or lower than 22 dB HL. The incidence of EOAEs decreased and EOAE thresholds increased with increasing click or mean audiometric thresholds.

High-frequency vestibulo-ocular reflex activation through forced head rotation in man.

The dynamic characteristics of the human vestibulo-ocular system were studied in the 0.5-30 Hz frequency range by rotating the head around a vertical axis. The rotation produced by a powerful servo-controlled vibrator was transmitted to the head by a hard-cushioned helmet and a rigid bite bar. The vestibulo-ocular reflex (VOR) gain and phase were measured during fixation of a mobile or stationary visual target and in total darkness. In a second set of experiments, the subjects evaluated the amplitude of the perceived visual instability of the target in the two fixation conditions. The results confirm earlier observations describing the VOR gain and phase in the 0.5-8 Hz range: the gain starts to decrease beyond 2 Hz and the phase rises towards 90 degrees. Beyond 8 Hz, the gain curve reverses direction and increases continuously toward 3-4 at 25-30 Hz in the three tested situations. Meanwhile, the phase curves do not vary much. In the same frequency range, the perceived visual instability is significantly altered. Therefore, the gain variation at high frequency may, in part, explain the perceived visual target instability and may be suspected of altering visually controlled tracking executed in vibrating environments.

[Development and training of monocular motor control]. / Développement et apprentissage du contrôle moteur monoculaire.

Misalignment of the visual axes of the eyes observed in strabismus may result from sensory, motor, and/or central nervous system disorders. The functional properties of a technique designed to increase, through training, the monocular motor control of normal human subjects was evaluated, the ultimate goal being obviously to apply the technique to cases of minor strabismus. The subject is seated in front of a television screen. A diaphragm extending from the subject's head to the screen divides the picture into two visually separated half fields. A micro-computer was programmed to project two patterns on the screen, made up of vertical green and grey bars (spatial frequency, 3 deg.). Displacement of the two visually superposable half fields could be independently achieved. The subject's task was to fixate, with one eye, the corresponding half field maintained stationary and track, with the other eye, the motion of the second half field. Perfect fusion of the two half fields has to be preserved during movements of the mobile half field over 2 to 6 degrees at a frequency of 0.4 Hz. The results show that after a few training sessions, subjects developed a high gain monocular motor control. This observation suggests that the method may be used as therapy to correct minor strabismus with or without anomalous retinal correspondence, and offers the possibility to study static and dynamic characteristics of Panum's areas and particularly their modifications as a function of training of monocular motor control.