The prognostic value of electrocochleography in severely hearing-impaired infants

This paper presents a longitudinal evaluation of electrocochleographic asse ssment in severely hearing-impaired infants. Electrophysiological data were obtained by transtympanic electrocochleography to tone-burst stimuli at oc tave frequencies of 500 to 8000 Hz at the age of 0-6 years in a group of 12 6 subjects. The results are compared with auditory thresholds determined at school age in the same children by means of purl-tone audiometry. Cochlear microphonics could be recorded in virtually all ears: although the majorit y of subjects had hearing losses of 90 dB and more. Compound action potenti als (CAPs) showed waveforms varying from normal to a wide range of abnormal ities. Audiometric thresholds correlated generally well with the compound a ction potential (CAP) thresholds obtained in infancy. The error in the pred icted audiometric thresholds is between 15 and 20 dB, as compared with 11 d B reported for more moderate hearing losses. It is shown that, in spite of the high stimulus levels used, substantial frequency-specific threshold inf ormation is retained. Occasional large discrepancies in thresholds were oft en associated with markedly abnormal response waveforms. Among the many cas es in which no ABR could be elicited, 68 per cent produced detectable elect rocochleographic responses in the 1000-4000 Hz range. It is concluded that electrocochleography is a valuable method for the assessment of residual he aring in infants suspected of having a severe hearing impairment.