A Longitudinal Study of Electrode Impedance, the Electrically Evoked Compound Action Potential, and Behavioral Measures in Nucleus 24 Cochlear Implant Users
- 1 December 2001
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Ear & Hearing
- Vol. 22 (6), 471-486
- https://doi.org/10.1097/00003446-200112000-00004
Abstract
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. 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. 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. 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.Keywords
This publication has 23 references indexed in Scilit:
- The Relationship Between EAP and EABR Thresholds and Levels Used to Program the Nucleus 24 Speech Processor: Data from AdultsEar & Hearing, 2000
- Comparison of EAP Thresholds with MAP Levels in the Nucleus 24 Cochlear Implant: Data from ChildrenEar & Hearing, 2000
- Does electrical stimulation of deaf cochleae prevent spiral ganglion degeneration?Hearing Research, 1999
- Summary of Results Using the Nucleus CI24M Implant to Record the Electrically Evoked Compound Action PotentialEar & Hearing, 1999
- Intracochlear Factors Contributing to Psychophysical Percepts Following Cochlear ImplantationActa Oto-Laryngologica, 1998
- Longitudinal Assessment of Physiological and Psychophysical Measures in Cochlear Implant UsersEar & Hearing, 1995
- Intraoperative and Postoperative Electrically Evoked Auditory Brain Stem Responses in Nucleus Cochlear Implant UsersEar & Hearing, 1994
- Long-Term Measures of Electrode Impedance and Auditory Thresholds for the Ineraid Cochlear ImplantJournal of Speech, Language, and Hearing Research, 1992
- Electrically evoked whole-nerve action potentials: Data from human cochlear implant usersThe Journal of the Acoustical Society of America, 1990
- Electrical Stimulation with Pt Electrodes: AMethod for Determination of "Real" Electrode AreasIEEE Transactions on Biomedical Engineering, 1977