Middle-ear reflex testing using wideband acoustic immittance

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PROJECT SUMMARY/ABSTRACT The objective of this project is to build and evaluate a middle-ear muscle reflex (MEMR) test system that is based on measurement of wideband acoustic immittance (WAI). This WAI-MEMR system will be accurate, scientifically and technically sound, stable, reliable, safe, and clinician friendly. Acoustically elicited MEMRs have a long history of value in the clinical evaluation of hearing loss. While sensitive to and affected by middle- ear disorders linked to conductive hearing losses, MEMRs also demonstrate particular sensitivity to synaptic and postsynaptic disorders related to the eighth nerve and auditory brainstem pathways through activation of neural pathways ipsilateral and contralateral to the physiologic middle-ear response. MEMRs are objective in providing information rapidly without requiring behavioral responses from the patient, and this objectivity facilitates their use in infants. Measuring MEMRs in the context of WAI provides clear advantages over current methods based on the ability to evaluate responses over a broader frequency range and to elicit responses to lower-intensity stimuli. The broadband nature of WAI is a well-documented advantage in infant testing. However, even though MEMR is a robust and sensitive measure, it is underutilized clinically on account of concerns that include subjectivity in response determination, intrasubject variation, uncertainty about MEMR response presence, and lack of confidence among clinicians in interpreting responses. The specific aims for this Phase II project are to (1) build a dual-probe WAI-MEMR system that is capable of ipsilateral, contralateral, and binaural stimulus paradigms and allows flexible and precise manipulation of test parameters; (2) develop automated processes for analyzing and quantifying WAI-MEMR responses to provide a method for objective test interpretation; (3) develop and test artifact rejection methods, a user-friendly probe, and calibration methods; (4) define stimulus and acquisition parameters further through human-subject testing of infants, children, and adults with normal hearing and with hearing loss; and (5) implement new paradigms and evaluate the new Phase II dual-channel system in adults and infants with normal hearing. The accomplishments completed during Phase I have resulted in a prototype dual-probe system that has been tested in adults with normal hearing and hearing loss with promising results. Work has begun toward automated analysis as well as defining frequency, amplitude, and threshold characteristics in infants and adults. The ongoing, productive collaboration between Dr. Jeng at Mimosa Acoustics and Dr. Hood at Vanderbilt University will continue throughout the Phase II project period for the development and evaluation of the WAI-MEMR approach. Creating hardware and software that uses this approach should reduce subjectivity in clinician interpretation and encourage increased clinical utilization and application in patients of all ages. In addition, the expanded capabilities that both WAI and a dual-probe system provide will foster advancement in understanding the characteristics of the MEMR in various populations and facilitate applications in clinical practices.