Longitudinal changes in electrical stapedius reflex thresholds (eSRT) in children with cochlear implants.

Abstract

Study goal: The electrically evoked stapedius reflex threshold (eSRT) is widely used as an estimate of the maximum comfort level (MCL) in the fitting of cochlear implants (CI). This study investigated the long-term evolution of the eSRT during a ten-year observation period.

Methods: Retrospective analysis of fitting map data (charge units [QU] required to evoke the stapedius reflex) obtained from 50 cochlear-implanted ears of 26 children. Time-series statistical methods were employed to examine trends in charge unit (QU) values and their variance, normalized to individual baselines.

Results: The QU time series mean increased significantly within the first six months post-implantation and reached a plateau thereafter. Variance in eSRT decreased significantly over the first five years, with three key turning points identified at six months, 18 months, and 4.25 years, indicating significantly diminishing variation with time.

Discussion: CI fitting schedules should be coordinated with temporal changes in eSRT variance. Frequent fittings in the first 18 months, followed by annual fittings until four years after implantation, seem advisable. After this period, less frequent fittings may be sufficient.