Click evoked Middle Ear Muscle Reflex: Implications for Medial Olivocochlear System Assays

This study describes a time series-based method of middle ear muscle reflex (MEMR) detection using bilateral clicks, with implications for otoacoustic emission (OAE)-based medial olivocochlear reflex (MOCR) assays. Although current click-based methods can detect changes in the OAE evoking stimulus to monitor the MEMR, these methods do not discriminate between true MEMR-mediated vs. artifactual changes in the stimulus. We measured MEMR in 20 young clinically normal hearing individuals using a series of clicks presented at six levels (65 to 95 dB peak-to-peak SPL in 6 dB steps). Results were well-approximated by double-exponential functions. The change in ear canal pressure due to MEMR increased monotonically as a function of click level but non-monotonically with frequency. MEMR thresholds estimated using this method were lower than that obtained from a clinical tympanometer in ~94% of the participants. It is recommended that the OAE-evoking stimulus be monitored to determine the presence of MEMR across a wide band of frequencies in MOCR assays. A time series-based method, along with statistical tests, may provide additional confidence in detecting the MEMR. MEMR effects were smallest at 2 kHz which may provide avenues for minimizing the MEMR influence on the MOCR.