Abstract
BackgroundAn electrical potential not previously reported—electrical cochlear response (ECR)—observed only in implanted patients is described. Its amplitude and growth slope are a measurement of the stimulation achieved by a tone pip on the auditory nerve. The stimulation and recording system constructed for this purpose, the features of this potential obtained in a group of 43 children, and its possible clinical use are described. The ECR is obtained by averaging the EEG epochs acquired each time the cochlear implant (CI) processes a tone pip of known frequency and intensity when the patient is sleeping and using the CI in everyday mode. The ECR is sensitive to tone pip intensity level, microphone sensitivity, sound processor gain, dynamic range of electrical current, and responsiveness to electrical current of the auditory nerve portion involved with the electrode under test. It allows individual evaluation of intracochlear electrodes by choosing, one at the time, the central frequency of the electrode as the test tone pip frequency, so the ECR measurement due to a variable intensity tone pip allows to establish the suitability of the dynamic range of the electrode current.ResultsThere is a difference in ECR measurements when patients are grouped based on their auditory behavior. The ECR slope and amplitude for the Sensitive group is 0.2 μV/dBHL and 10 μV at 50 dBHL compared with 0.04 μV/dBHL and 3 μV at 50dBHL for the Inconsistent group. The clinical cases show that adjusting the dynamic range of current based on the ECR improved the patient’s auditory behavior.ConclusionsECR can be recorded regardless of the artifact due to the electromyographic activity of the patient and the functioning of the CI. Its amplitude and growth slope versus the intensity of the stimulus differs between electrodes. The relationship between minimum ECR detection intensity level and auditory threshold suggests the possibility of estimating patient auditory thresholds this way. ECR does not depend on the subject’s age, cooperation, or health status. It can be obtained at any time after implant surgery and the test procedure is the same regardless of device manufacturer.
Highlights
An electrical potential not previously reported—electrical cochlear response (ECR)—observed only in implanted patients is described
The relationship between minimum ECR detection intensity level and auditory threshold suggests the possibility of estimating patient auditory thresholds this way
Estimating patient’s T and C/M psychophysical levels based on the evoked compound action potential (eCAP) threshold may be affected by the change of pulse width and stimulation rate when patient uses the device in everyday mode, in addition to the summating effect which contiguous stimulation pulses has on auditory nerve response [16, 20]
Summary
An electrical potential not previously reported—electrical cochlear response (ECR)—observed only in implanted patients is described. The ECR is sensitive to tone pip intensity level, microphone sensitivity, sound processor gain, dynamic range of electrical current, and responsiveness to electrical current of the auditory nerve portion involved with the electrode under test. Except the eCAP, the electrical stimulating pulses are similar to those used in programming the CI, obtaining the auditory system response as a change of immittance in the ear contralateral to the CI, as in the eSRT case, or as a single-channel electrical recording in differential mode using surface electrodes, in the case of the eABR These objective measurements help to predict the limit values of the dynamic range of stimulating electrical current, which, applied through intracochlear electrodes, ideally gives the patient useful, comfortable, and safe hearing. Some reasons which limit the CI user’s ability to detect and discriminate sounds are the health status of the implanted cochlea, which results in variations of sensitivity to electrical current depending on the region stimulated, in addition to the parameters used to configure the stimulating electrical current [6,7,8,9,10]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
