Brain stem responses evoked by stimulation with an auditory brain stem implant in children with cochlear nerve aplasia or hypoplasia
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Published on: January 9, 2019
Martin O'Driscoll1, Wael El-Deredy, Ahmet Atas
1Auditory Implant Programme, University of Manchester, United Kingdom. martin.odriscoll@manchester.ac.uk
Insights
Electrically evoked auditory brain stem responses (EABRs) help locate auditory brain stem implant (ABI) electrodes in children. Postoperative EABR thresholds correlate with behavioral levels, aiding initial device fitting for congenital deafness.
Area of Science:
- Audiology
- Neuroscience
- Biomedical Engineering
Background:
- Auditory brain stem implants (ABIs) are increasingly used for children with congenital deafness.
- Fitting ABIs in this population presents challenges, necessitating objective measures.
- Intraoperative electrically evoked auditory brain stem responses (EABRs) can guide surgical placement and device programming.
Purpose of the Study:
- Characterize EABRs in children stimulated via ABI.
- Compare intraoperative and postoperative EABRs.
- Assess EABR morphology variations with stimulation site.
- Correlate EABRs with behavioral outcomes and perceived sensations.
Main Methods:
- Recorded intra- and postoperative EABRs in six congenitally deaf children (mean age 4.2 years).
- Stimulated nine bipolar sites on the ABI array, analyzing EABR morphology and latency.
- Investigated EABR relationship with auditory electrode presence.
- Compared EABR thresholds with behavioral (T and C) levels.
Main Results:
- EABRs were elicited in all children, with 1-3 peaks observed.
- EABRs predicted auditory responses but their absence did not reliably predict non-response.
- EABR morphology varied by stimulation site and test occasion.
- Postoperative EABR thresholds correlated well with behavioral T and C levels.
Conclusions:
- Intraoperative EABRs indicate effective electrode placement for auditory sensation.
- EABR morphology can be variable.
- Postoperative EABR thresholds are valuable for initial ABI device fitting in children.
Objectives:
The inclusion criteria for an auditory brain stem implant (ABI) have been extended beyond the traditional, postlingually deafened adult with Neurofibromatosis type 2, to include children who are born deaf due to cochlear nerve aplasia or hypoplasia and for whom a cochlear implant is not an option. Fitting the ABI for these new candidates presents a challenge, and intraoperative electrically evoked auditory brain stem responses (EABRs) may assist in the surgical placement of the electrode array over the dorsal and ventral cochlear nucleus in the brain stem and in the postoperative programming of the device. This study had four objectives: (1) to characterize the EABR by stimulation of the cochlear nucleus in children, (2) to establish whether there are any changes between the EABR recorded intraoperatively and again just before initial behavioral testing with the device, (3) to establish whether there is evidence of morphology changes in the EABR depending on the site of stimulation with the ABI, and (4) to investigate how the EABR relates to behavioral measurements and the presence of auditory and nonauditory sensations perceived with the ABI at initial device activation.
Design:
Intra- and postoperative EABRs were recorded from six congenitally deaf children with ABIs, four boys and two girls, mean age 4.2 yrs (range 3.2 to 5.0 yrs). The ABI was stimulated at nine different bipolar sites on the array, and the EABRs recorded were analyzed with respect to the morphology and peak latency with site of stimulation for each recording session. The relationship between the EABR waveforms and the presence or absence of auditory electrodes at initial device activation was investigated. The EABR threshold levels were compared with the behavioral threshold (T) and comfortably loud (C) levels of stimulation required at initial device activation.
Results:
EABRs were elicited from all children on both test occasions. Responses contained a possible combination of one to three peaks from a total of four identifiable peaks with mean latencies of 1.04, 1.81, 2.61, and 3.58 msecs, respectively. The presence of an EABR was a good predictor of an auditory response; however, the absence of the EABR was poor at predicting a site with no auditory response. The morphology of EABRs often varied with site of stimulation and between EABR test occasions. Postoperatively, there was a trend for P1, P3, and P4 to be present at the lateral end of the array and P2 at the medial end of the array. Behavioral T and C levels showed a good correlation with postoperative EABR thresholds but a poor correlation with intraoperative EABR thresholds.
Conclusions:
The presence of an intraoperative EABR was a good indicator for the location of electrodes on the ABI array that provided auditory sensations. The morphology of the EABR was often variable within and between test sessions. The postoperative EABR thresholds did correlate with the behavioral T and C levels and could be used to assist with initial device fitting.
