Aspects Inherent To The Recovery Function Of The Auditory Nerve On The Speech Processing In Noise In Patients With Cochlear Implants

Background: Cochlear Implant (CI) partially replaces the functions of the cochlea, converting sound energy into electrical signals, enabling electrical stimulation of the auditory nerve and transmission to the cerebral cortex. This study investigates auditory nerve Recovery Time (REC) and introduces the Frequency Following Response (FFR) with stimulus |da| as tools to assess auditory system integrity in CI users, particularly concerning speech perception in quiet and noise. This research aims to explore the correlation between REC, neural conduction in the brainstem, and speech recognition performance in CI users, contributing to the understanding and enhancement of this technology. Materials and Methods: This was a prospective, cross-sectional, exploratory study, approved by the Institutional Review Board (IRB) of the hospital where the study was conducted. It involved 06 adults with postlingual deafness who underwent cochlear implant surgery, three women (mean age 67 years) and three men (mean age 70 years), three right ears and three left ears. Participants exhibited free-field auditory thresholds not exceeding 25dBHL from 250Hz to 6000Hz, with 70% speech recognition in quiet, stable electrode impedances, and present neural response (evoked compound action potential). Data collection included sentence recognition in quiet and noise, recovery time parameters involving absolute refractory period "T0," relative refractory period "tau", and saturation amplitude "A", assessed in three cochlear regions (apical electrode 16, medial electrode 11, and basal electrode 6). FFR included the investigation of wave "V" and valleys "A, C, D, E, F, and O”. Results: The results revealed moderate to strong positive and negative correlations between REC parameters, FFR latencies, and speech recognition in quiet and noise. Statistically significant correlations were particularly observed between REC ("T0, tau, and A"), in electrodes 11 and 6, and valleys "D and E". Conclusion: This study demonstrated statistical correlation between auditory nerve recovery time and brainstem neural conduction for speech in CI users