Normative Ranges for Wideband Middle Ear Muscle Reflex Magnitude: Limited Potential for Diagnosing Cochlear Deafferentation
Description
In a population at low risk for cochlear synaptopathy due to young age, normal hearing thresholds, and minimal noise exposure history, this study generated normative ranges for middle ear muscle reflex (MEMR) magnitude. The normative ranges were statistically adjusted for average distortion product otoacoustic emission (DPOAE) levels to account for possible impacts of outer hair cell dysfunction. To evaluate the ability of the normative ranges to differentiate between populations at low versus high risk of synaptopathy, MEMR and DPOAE measurements were also collected from military Veterans with normal hearing thresholds who reported at least one of the auditory complaints predicted to result from synaptopathy – tinnitus, speech perception in noise difficulty, or decreased sound tolerance. For individuals with poorer DPOAEs, it was not possible to fall below the lower bounds of the wideband MEMR normative ranges. For individuals with more robust DPOAEs, the lower bounds are very close to an MEMR magnitude indicating an absent reflex. Few individuals from the high-risk sample fell below the normative ranges, suggesting that these normative ranges do not identify significant cochlear deafferentation as expected.