Congratulations to Sriram Boothalingam, Ph.D., FAAA, on receiving a 2018 American Speech-Language-Hearing Foundation New Century Scholars Research Grant for his project “One Stone, Three Birds: A Concurrent Clinical Test of Cochlear, Middle Ear Muscle Reflex, and Medial Olivocochlear Reflex Function”.
Peripheral synaptopathy or hidden hearing loss (HHL), induced by exposure to even moderate levels of noise, is undetectable by any traditional clinical audiological measure. As such, there is a critical demand for an objective clinical test that is sensitive to peripheral synaptopathy in humans. Unfortunately, electrophysiological and behavioral assays that were thought to tap into the specific noise-prone synaptic damage have not yet produced conclusive results. However, the middle ear muscle reflex (MEMR) and the medial olivocochlear reflex (MOCR) may have diagnostic value in synaptopathy. Specifically, larger noise exposure is related to elevated MEMR thresholds and increased MOCR activity in humans, corroborating findings in animal models. Given the sensitivity of both MEMR and MOCR to suspected (s)synaptopathy, we argue that a combined test of MEMR and MOCR would be a valuable tool in the screening and diagnosis of synaptopathy. However, current MOCR tests are recommended against clinical use as they only the contralateral reflex pathway of the bilateral reflex and their have sub-par repeatability. We have developed a test that uses clicks and click-evoked otoacoustic emissions (CEOAEs) to concurrently monitor MOCR and MEMR. By using the same clicks that evoke OAEs, to also elicit MOCR and MEMR, we were able to conduct the test bilaterally. In addition to the magnitude, our method estimates the kinetics of the two reflexes. In the two proposed studies, we will (i) establish the test-retest repeatability of our novel test and (ii) test whether the novel assay is sensitive to changes in the auditory system due to noise exposure. Findings will facilitate translation of the test to clinical settings, and may help in the evaluation of auditory disorders such as HHL, auditory neuropathy, tinnitus, hyperacusis, and auditory processing disorders.