This reporting year, 63 patient visits (of healthy normal subjects) were completed in fulfillment of the ongoing need to develop normal (clinically essential) values for upgraded brainstem auditory evoked potential software. This normative data base permits valid and reliable comparisons and clinical judgements for individual patients, highly specialized patient groups and patient populations relevant to NIDCD (and other NIH) protocols. With the arrival of new evoked potential equipment, it will be necessary to generate new absolute and interpeak data points for both circumaural and insert earphones. These data are gathered and analyzed by gender for ages 2 through 50 and by decade from 50 through 80. We have continued the work begun last year gathering normative data on age and sex matched controls for the study of multi-frequency immittance. Development of normative data on the current instrument has proceeded in normally hearing individuals between 15 and 50 years of age with a consistent effort to always use equal numbers of males and females. Other patient groups studied using multi-frequency tympanometry include patients with and, or at risk for, Osteogenesis Imperfecta (OI). Earlier two frequency tympanometry studies in OI patients, first degree relatives and possible carriers revealed significant and diverse abnormalities in middle ear biomechanics, suggesting the need for this investigation. We are still planning to compare data developed from multifrequency immittance studies to those generated using otoadmittance paradigms. As has now become clear, the study of middle ear biomechanics and its clinical applications require more data on normal function. It is important to be able to understand the mechanisms underlying clinical findings in patients with various types of musculoskeletal disease as well as clinical manifestations of aging in the middle ear system. To that end, we look forward to studying more subjects over age 50 in the coming year. Specific data derived from studies of middle ear response on normals of both sexes and across age groups is necessary to begin clinical comparisons with a wide variety of connective tissue disorders including arthritis of various forms, osteogenesis imperfecta, and others. The study of cochlear emissions in normals has continued and expanded in this reporting period. Data collection has now begun in certain populations of relevance to NIDCD. Using KEMP IL088 instrumentation, click evoked emissions data are also being collected in Waardenburg patients, patients with Thalassemia and Type 2 Neurofibromatosis. Developing normal values in various emission techniques is becoming important as more and more clinics and laboratories come on line using this promising new clinical tool. Our future clinical research in cochlear emissions will include newer applications and approaches including suppression of emissions by contralateral signals (in the evaluation of interhemispheric auditory function); distortion product emissions (for evaluating hearing loss thought to be due to outer hair cell damage; stimulus frequency emissions (may be of interest in aging studies) and amplitude/intensity functions to evaluate cochlear potential. This past year has been a burgeoning of clinics and laboratories using cochlear emissions in this country. This technology may offer significant advantages and insights previously unavailable in studying auditory system function in the living human being through non-invasive techniques accomplished with remarkable speed.
