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Assessment of the functioning of peripheral auditory pathways after cochlear re-implantation in young children using
S M Mason1, M Dodd, K P Gibbin
1Medical Physics Department, Queen's Medical Centre, Nottingham, UK. Steve.Mason@nottingham.ac.uk
Insights
Cochlear re-implantation in children shows preserved neuronal function, with intra-operative measures like electrical auditory brainstem response (EABR) indicating survival. However, EABR thresholds may underestimate post-operative hearing sensitivity.
Area of Science:
- Audiology
- Neuroscience
- Pediatric Otolaryngology
Background:
- Cochlear re-implantation is necessary after initial device failure.
- Assessing neuronal function post-re-implantation is crucial for auditory rehabilitation.
Purpose of the Study:
- To objectively evaluate the impact of cochlear re-implantation on intra-operative electrophysiological measures.
- To investigate neuronal function and auditory nerve survival in pediatric patients undergoing re-implantation.
Main Methods:
- Recorded intra-operative electrical auditory brainstem response (EABR) and electrical stapedius reflex threshold (ESRT).
- Measured early post-operative behavioral threshold levels (T-levels) for electrical stimulation.
- Analyzed amplitude input/output (I/O) functions and thresholds in five pediatric patients.
Main Results:
- EABR and ESRT patterns were consistent with expected responses during both first and second implantations.
- Amplitude I/O function slopes for EABR wave eV remained similar post-re-implantation.
- Intra-operative thresholds generally elevated after re-implantation, more so than behavioral T-levels.
Conclusions:
- Cochlear re-implantation demonstrates a high degree of neuronal survival.
- Intra-operative EABR thresholds at re-implantation may underestimate the patient's actual hearing sensitivity measured by post-operative T-levels.
Abstract:
The intra-operative electrical auditory brainstem response (EABR), electrical stapedius reflex threshold (ESRT) and the early post-operative behavioural threshold level (T-level) were recorded in five children undergoing cochlear re-implantation. The aim of the study was to assess objectively the effect of re-implantation on intra-operative objective measures and to investigate neuronal function. The children were aged between 2.06 years and 4.5 years at first implantation. Following failure of the first device, re-implantation was carried out 1.42-5.52 years later. Characteristics of the EABR and ESRT across the electrode array were typical of the expected pattern of responses on both occasions. In particular, the slopes of the amplitude input/output (I/O) functions for wave eV of the intraoperative EABR were similar for both the first and second implants even though absolute thresholds were generally elevated after re-implantation. This elevation in intra-operative threshold was more pronounced than the change in early post-operative behavioural threshold level for electrical stimulation (T-level). Our findings confirm a high level of neuronal survival after re-implantation. Threshold of the intra-operative EABR at the time of re-implantation greatly underestimates the sensitivity of the subsequent early post-operative T-levels.