LOW-FREQUENCY SENSORINEURAL LOSS - CLINICAL-EVALUATION AND IMPLICATIONS FOR HEARING-AID FITTING

Spread of excitation in the cochlea places fundamental limits on the i nterpretation of audiometric pure-tone hearing loss as a simple map of dysfunction along the cochlear partition, and histologic evidence fro m human temporal bones will be presented to demonstrate the insensitiv ity of the audiogram to variations in pathology in the case of low-fre quency hearing loss. This article will describe a clinical procedure u sing simultaneous pure-tone masking to improve upon the localization o f cochlear disease, particularly for low-frequency hearing losses, and a model for using the Articulation Index (AI) to develop prognoses fo r hearing aid performance in these cases, which can then be tested. Fo urteen patients with low-frequency hearing loss were divided into two groups based upon threshold shifts caused by a pure-tone masker: those that showed normal low-frequency threshold shifts and those that show ed marked shifts at frequencies below the masker, indicating greater l oss of function than shown by the unmasked audiogram. Hypothetical aud iograms were then generated to model a complete loss of apical functio n for all patients. Measured speech recognition scores were then compa red to AI predictions for the actual and hypothetical audiograms. Best agreement for the patients showing normal masking shifts was between the measured scores and the AI for the actual audiogram, whereas the b est agreement for the patients showing marked shifts was with the AI f or the hypothetical audiogram. The implications for hearing aid recomm endation and fitting in these cases are discussed.