Acoustic Impedance Measures in the Down's Population

Abstract

Impedance audiometry has proved to be especially valuable in the auditory evaluation of difficult-to-test children—including those youngsters with Down's syndrome. The impedance technique is extremely sensitive in differentiating between normal and pathologic middle ears. Impedance measurements, especially tympanometry and acoustic reflex testing, may be used prior to traditional audiometric tests so that the clinician will know what type of hearing impairment to anticipate. Some clinicians prefer to perform tympanometry and acoustic reflex measurement following routine audiometry to confirm pure tone results. In either case, acoustic impedance measurements provide important information concerning the otologic status of all pediatric patients. The Down's child certainly has many potential reasons for presenting with conductive-type hearing impairment. Ear symptoms commonly associated with Down's include small pinnae, narrow external auditory canals, abnormal external ear configuration, and a strong tendency to have otitis media (Rigrodsky, Prunty, and Glovsky, 1961). In addition, it has been suggested that the Down's child may be more susceptible to upper respiratory tract infections than the normal child because of peculiar skull development, which can adversely affect proper drainage of the sinuses and middle-ear spaces (Mclntire, Menolascino, and Wiley, 1965). Thus, with the numerous difficulties that may be encountered when performing routine audiometry with mentally retarded children, impedance measurements often confirm or rule out the presence of conductive-type hearing disorder.