The Relationship Between eSRTs and Upper Stimulation Levels in a Large Cohort of Adult Cochlear Implant Recipients

Abstract

Objective: To compare electrically evoked stapedial reflex thresholds (eSRTs) measured at 1 month post-activation to upper stimulation levels used for programming adult cochlear implant (CI) recipients over time in a large clinical population.

Study design: Review of prospectively collected clinical database.

Setting: Large CI program at an academic medical center.

Patients: Postlingually deafened adult CI recipients (n = 439).

Main outcome measures: eSRTs recorded in the medical record and upper stimulation levels derived from the programming software at 1 and 6 months post-activation.

Results: The correlation between eSRTs and upper stimulation levels was strong for all three manufacturers (r = 0.80-0.86). On average, upper stimulation levels were set 15.4 clinical levels below eSRT for Cochlear using a pulse width of 25 microseconds, 13.4 clinical levels below eSRT for Cochlear using a pulse width of 37 microseconds, 11.3 clinical units below eSRT for Advanced Bionics, and 0.1 charge unit above eSRT for MED-EL. eSRTs were found to be elicited at similar levels for different electrodes/frequencies across the array. After upper stimulation levels were set based on eSRT at 1 month post-activation, there was no significant change in upper stimulation levels between 1 and 6 months post-activation.

Conclusions: eSRTs and upper stimulation levels are highly correlated. Average differences between eSRTs and upper stimulation levels reported herein can be used to guide programming in the clinic. Further, when eSRTs are used to program upper stimulation levels, upper stimulation levels should be relatively similar across channels and stable over time.