Danielle M. R. Kelsay

A longitudinal study of electrode impedance, the electrically evoked compound action potential, and behavioral measures in nucleus 24 cochlear implant users.

Objective The primary goal of this study was to examine changes that may occur in electrode impedance, electrically evoked compound action potential (EAP) threshold and slope of the EAP growth function, and behavioral measures of threshold (MAP T-level) and maximum comfort (C-level) over time in both adult and child cochlear implant users. Secondary goals were to determine whether changes in these measures are consistent between children and adults, and to determine whether behavioral measures (MAP T- and C-levels) and electrophysiologic measures (EAP thresholds) exhibit the same trends over time. Design Thirty-five children and 33 adults implanted with the Nucleus CI24M between November 1996 and August 1999 participated in this study. Subjects were included in this study if 1) they had used their implant for at least 1 yr after device connection, and 2) they had participated in the necessary data collection at a minimum number of the time intervals assessed in this study. EAP threshold, slope of the EAP growth function, and common ground electrode impedance measures were collected intraoperatively, at initial stimulation, and at several subsequent visits up to 2 yr post initial stimulation. MAP T- and C-levels were measured at initial stimulation and at the same time intervals as described above. Results Changes in electrode impedance, EAP thresholds, and slope of the EAP growth function from measures made intraoperatively, at initial stimulation, and at 1 to 2 mo post initial stimulation were similar in both children and adults. Beyond the 1- to 2-mo visit, children exhibited significant increases in electrode impedance, EAP thresholds, slope, and MAP T-levels, whereas these same measures in adults remained relatively stable. EAP thresholds in children stabilized by the 3- to 8-mo visit, and electrode impedance stabilized by the 6- to 8-mo visit, while slope of the EAP growth function, MAP T-levels, and MAP C-levels were stable by 1 yr post initial stimulation. C-levels in adults increased up to 1 yr post initial stimulation; however, the amount of increase was much smaller than that seen in children. In both children and adults, longitudinal trends in EAP thresholds mirrored T-level more closely than C-level. Conclusions The results of this study suggest that peripheral changes occur in many children that do not generally occur in adults within the first year of cochlear implant use. One implication of these results is that if EAP thresholds are to be used to assist in programming the speech processor for children, it is best to make those measures at the same time interval as device programming rather than using measures made intraoperatively or at the initial programming session to set MAP levels at later visits.

Speech perception by prelingually deaf children using cochlear implants.

In this investigation we measured the performance of 50 prelingually deaf children on several speech perception tests. Children were from 2 to 15 years of age, and some children were tested with as much as 5 years of cochlear implant use. Speech perception tests included the recognition of stress pattern, consonants, vowels, words, and sentences. The audiovisual perception of consonants was also measured. Average results indicated that gains were being made in the perception of stress and words in a closed-set context within 1 year from implantation. The perception of words in an open-set context demonstrated much slower increases over time. Large individual differences were observed. Some preliminary data suggest that children who receive implants before the age of 4 years obtain higher scores, on average, than children who receive implants after the age of 5 years. Some children become part-time users or nonusers of their cochlear implants. The average results from 18 congenitally deaf children were significantly higher than the average results from 12 children with prelingually acquired deafness after 3 years of implant use. Information on vowel and consonant features shows increases in performance after 2 years of cochlear implant use, with the exception of the place feature. For this feature, no changes were observed. Vision-alone testing indicated that lipreading performance increased over time. An audiovisual enhancement provided by the cochlear implant was observed for all features.

Intraoperative and postoperative electrically evoked auditory brain stem responses in nucleus cochlear implant users: Implications for the fitting process

Electrically evoked auditory brain stem responses (EABR) were measured in 12 adults and 14 children with the Nucleus cochlear implant. Measures were made both intra operatively and several months following surgery. EABR thresholds were consistently greater than clinically determined measures of behavioral threshold (T-level) but less than maximum comfort levels (C-level). When the data were pooled across subjects and different stimulating electrodes, EABR thresholds were strongly correlated with both T- and C-levels. In subjects where both intraoperative and postimplant EABR measures were obtained, intraoperative EABR thresholds were consistently higher than postimplant thresholds. The electrophysiologic data have been incorporated into a practical procedure for programming the implant in young children.

Speech perception by prelingually deaf children after six years of Cochlear implant use: effects of age at implantation.

From the Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa. Supported (in part) by a research grant awarded to the Department of Otolaryngology-Head and Neck Surgery, University of Iowa (No. 2 P50 DC 00242), from the National Institutes of Health/National Institute on Deafness and Other Communication Disorders; grant RR00059 from the General Clinical Research Centers Program, Division of Research Resources, National Institutes of Health; the Lions Clubs International Foundation; and the Iowa Lions Foundation.

Pre‐lingually deaf children can perform as well as post‐lingually deaf adults using cochlear implants

Abstract Both pre-lingually deaf children and post-lingually deaf adults benefit from cochlear implants. These adults have a memory for speech sounds, but the children do not. In this preliminary investigation, we asked whether it was possible for these children to obtain high scores similar to the adults. We compared 21 pre-lingually deaf children to 81 post-lingually deaf adults using multichannel cochlear implants on the same test of sentence recognition. The children were selected to have the vocabulary and language sufficient to complete the test. Scores from the children, ranged from 0 to 97% correct. About one half of the children scored above 70% correct. Scores from the adults ranged from 0 to 100% correct with about one half of the adults scoring over 60%. Many of the children are scoring as well or better than adults are scoring. We conclude that the auditory system of pre-lingually deaf children is sufficient to obtain levels of speech recognition similar to postlingually deaf adults

Speech feature perception in prelingual deaf children with cochlear implants.

The speech‐perception abilities of 15 prelingual deaf children, using the Nucleus 21‐channel cochlear implant, were examined with a new audiovisual speech‐feature test for young children. The test stimuli include the letters ‘‘b, d, c, p, t, v, z’’ and pictures of ‘‘me,’’ ‘‘knee,’’ and ‘‘key.’’ Preliminary test retest data suggest good reliability for a 60‐item test. Performance is significantly correlated with a closed‐set picture test for young children. A feature analysis indicated that the voicing and envelope features were understood moderately well when presented by audition, and the place feature was understood well when presented by vision. [Work supported by NIH.]