Electrically Evoked Auditory Event-Related Responses in Patients with Auditory Brainstem Implants

Shuman He, Tyler C. McFayden, Holly F. B. Teagle, Matthew Ewend, Lillian Henderson, Craig A. Buchman
2016 Ear and Hearing  
Objective-This study aimed to 1) characterize morphological characteristics of the electricallyevoked cortical auditory event-related potentials (eERP) and explore the potential association between onset eERP morphology and auditory vs non-auditory stimulation; 2) assess test-retest reliability of onset eERPs; 3) investigate effects of stimulation level on onset eERPs; and 4) explore the feasibility of using the onset eERP to estimate the lowest stimulation level that can be detected for
more » ... ual stimulating electrodes in patients with auditory brainstem implants (ABIs). Design-Study participants included five children (S1-S5) and two adults (S6-S7) with unilateral Cochlear Nucleus 24M ABIs. Pediatric ABI recipients ranged in age from 2.6 to 10.2 years (mean: 5.2 years) at the time of testing. S6 and S7 were 21.2 and 24.6 years of age at the time of testing, respectively. S6 and S7 were diagnosed with neurofibromatosis II (NF2) and implanted with an ABI after a surgical removal of the tumors. All pediatric subjects received ABIs after being diagnosed with cochlear nerve deficiency. The lowest stimulation level that could be detected (behavioral T level) and the estimated maximum comfortable level (C level) was measured for individual electrodes using clinical procedures. For electrophysiological measures, the stimulus was a 100-ms biphasic pulse train that was delivered to individual electrodes in a monopolarcoupled stimulation mode at stimulation levels ranging from sub-threshold to C levels. Electrophysiological recordings of the onset eERP were obtained in all subjects. For studies evaluating the test-retest reliability of the onset eERP, responses were measured using the same set of parameters in two test sessions. The time interval between test sessions ranged from two to six months. The lowest stimulation level that could evoke the onset eERP was defined as the objective T level. Results-Onset eERPs were recorded in all subjects tested in this study. Inter-and intra-subject variations in morphological characteristics of onset eERPs were observed. Onset eERPs with complex waveforms were recorded for electrodes that evoked non-auditory sensations, based on feedback from subjects, as well as for electrodes without any indications of non-auditory stimulations. Onset eERPs in patients with ABIs demonstrated good test-retest reliability. Increasing stimulation levels resulted in increased eERP amplitudes but showed inconsistent effects on response latencies in patients with ABIs. Objective and behavioral T levels were correlated. Conclusions-eERPs could be recorded in both non-NF2 and NF2 patients with ABIs. eERPs in both ABI patient groups show inter-and intra-subject variations in morphological characteristics. However, onset eERPs measured within the same subject in this study tended to be stable across study sessions. The onset eERP can potentially be used to estimate behavioral T levels in patients with ABIs. Further studies with more adult ABI recipients are warranted to investigate whether the onset eERP can be used to identify electrodes with non-auditory stimulations. Keywords Auditory brainstem implant; electrically-evoked cortical auditory event-related potentials; auditory detection threshold He et al.
doi:10.1097/aud.0000000000000342 pmid:27579988 pmcid:PMC5079768 fatcat:wwzmn7lylbhprpnh23ktxd3kui