The Relationship Between the Electrically Evoked Stapedius Reflex Threshold and Stimulus Burst Duration in Pediatric...

The electrically evoked stapedius reflex threshold (eSRT) is an objective measure that helps to fit cochlear implants (CIs). The primary aim of this study was to investigate the relationship between different burst durations to elicit eSRT in pediatric CI users.

Different stimuli burst durations (100-500 ms) were applied to observe the effect in the reflex determination in 11 pediatric CI users. Reflexes were measured in electrode contacts #2, #6, #9, and #11. Testing was conducted at 9 months after CI activation.

Burst duration and electrode contact site both had a significant effect on eSRT (p < 0.001). The lowest eSRT thresholds were obtained with the longest burst duration. The highest stimulation level was required to elicit a reflex at basal electrode contacts. No significant effect was found for the interaction between electrode contact site and burst duration.

Burst durations of 100 ms yielded significantly larger eSRT thresholds than 300- and 500-ms burst durations. Thresholds obtained with the longest (i.e., traditional) burst durations reflected maximum comfortable loudness (MCL) levels typically found at early post-activation stages. In contrast, 100-ms burst yielded threshold levels similar to MCLs that have stabilized. We therefore consider both short (100 ms) and longer (300 or 500 ms) bursts useful in the clinical practice.

The best burst duration to use depends on the interval: longer burst durations are useful for estimating MCLs for earlier intervals, whereas shorter burst durations are useful for later intervals. These findings may help clinicians optimize fittings in cases where using behavioral responses is problematic.