Stapedius reflex thresholds obtained in a free sound field as an indicator for over- and understimulation in cochlear implant listeners.

Objective: The goal of this study was to determine open field stapedius reflex thresholds (oSRTs) in CI patients with fittings based on subjective loudness ratings. A further objective was to compare these oSRTs and those of eSRT-based fittings that are similar to the oSRTs of normal hearing.

Design: Impedance measurements of the ear drum were taken while subjects were wearing their audio processors. The stapedius reflex was elicited by electrical stimulation transmitted through the activated CI system in response to an acoustic stimulus presented in the free sound field.

Study sample: Subjects were 50 experienced CI users (n = 57 ears) with CI fittings based on subjective loudness scaling.

Results: A reference range for the oSRTs was defined that was identified in CI patients with eSRT-based fittings. Sound levels for stapedius reflex detection were inside the reference target range in 70% of the cases, below the reference range (i.e. down to 40 dB HL) in 20% of the cases, and above the reference range in 10% of the cases.

Conclusion: Stapedius reflex detection in a free sound field may help detect fittings with too high or too low stimulation levels that might reduce audiological performance.