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Updated: Nov 25, 2025
Cochlear Implant Surgery and Electrically-evoked Auditory Brainstem Response Recordings in C57BL/6 Mice
Published on: January 9, 2019
Changes in electrically evoked auditory brainstem responses in children with sequential bilateral cochlear implants
Burcu Deniz1, Eyyup Kara1, Zahra Polat2
1İstanbul University-Cerrahpaşa, Faculty of Health Sciences, Department of Audiology, İstanbul, Turkey.
Insights
Electrically evoked auditory brainstem responses (eABR) show differences between first and second cochlear implants (CI1 vs. CI2) in young children. Further study is needed to evaluate long-term interaural differences in cochlear implant performance.
Area of Science:
- Pediatric audiology
- Neuroscience
- Otolaryngology
Background:
- Sequential cochlear implantation (CI) is common in young children with bilateral hearing loss.
- Understanding interaural differences in auditory brainstem responses is crucial for optimizing CI outcomes.
- Electrically evoked auditory brainstem responses (eABR) provide insights into auditory pathway function.
Purpose of the Study:
- To investigate differences in eABR between the first (CI1) and second (CI2) cochlear implants in young children.
- To assess changes in eABR parameters over six months post-implantation of the second CI.
- To evaluate the relationship between eABR findings and language development.
Main Methods:
- Thirteen children under five years old with sequential CIs participated.
- Postoperative eABRs were recorded at 1, 3, and 6 months after the second CI fitting.
- eABRs were measured for both CIs (CI2 then CI1) at basal, medial, and apical electrode positions.
Main Results:
- CI2 showed significantly longer eV wave latencies and lower amplitudes compared to CI1.
- Significant changes in eV latency and amplitude were observed over six months, particularly in the medial electrode.
- Sound field thresholds and language scores improved significantly in all subjects.
Conclusions:
- Postoperative eABR is valuable for assessing CI performance and auditory pathway function.
- Six months is insufficient to fully evaluate interaural differences due to ongoing neural maturation.
- Longer follow-up is necessary to understand the long-term development of auditory function in sequentially implanted children.
Objectives:
The primary aim of this study is to investigate whether the electrical stimulation of the second ear causes a difference in electrically evoked auditory brainstem responses (eABR) between two ears over time.
Methods:
The study included thirteen subjects under the age of five who used cochlear implants for at least six months in the first ear prior to the sequential cochlear implantation. Postoperative eABRs were conducted on the 1st (first fitting of the second speech processor), 3rd, and 6th months of the second implantation in the basal, medial, and apical electrode positions. The recording was started with the second cochlear implant (CI2), and then the first cochlear implant (CI1) was tested. Sound field audiometry and receptive/expressive language assessments were also performed at 1 and 6 months after the second cochlear implantation.
Results:
eABR results indicate that when eV wave latencies are examined for all electrodes, CI2 is significantly longer than CI1 (p < 0.05). When eV wave amplitudes are examined for all electrodes, CI1 is significantly higher than the CI2 (p < 0.05). eV latency and amplitude changes between both implants were examined up to six months after implantation. Statistically significant changes were observed in the basal, medial, apical electrode for eV wave latencies, and only in the medial electrode for eV wave amplitudes (p < 0.05). Average sound field thresholds and receptive/expressive language scores improved statistically significantly for all subjects at the end of the study (p < 0.05).
Conclusion:
The postoperative eABR test is a valuable test battery that provides the clinician with important ideas about the estimated threshold, comfortable and audible sound level, CI performance, and auditory pathways up to the brainstem. Since the maturation is still ongoing, an extended period longer than six months is needed to evaluate interaural differences.
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