Long-term audiometric follow-up of click-evoked auditory brainstem response in hearing impaired infants

Conventional pure-tone thresholds were collected as determined at ages betw een 4 and 8 years from a group of 163 infants, tested by auditory brainstem response (ABR) in the age range between 1 and 3 years old for objective he aring assessment. The subjects suffered from a variety of degrees and types of sensorineural hearing impairment. The prognostic value of the ABR peak V thresholds in response to 0.1 ms clicks with respect to the behavioural t hresholds at octave frequencies from 125 to 8,000 Hz obtained later is eval uated. Correlation between ABR and behavioural thresholds is largest in the 1,000- to 8,000-Hz frequency range. Predicted pure-tone audiograms (mean a nd SD) were determined for each 10-dB class of ABR thresholds. SDs are in t he order of 15 to 18 dB in the 500- to 4,000-Hz range and slightly higher a t adjacent frequencies (i.e., somewhat larger than in comparable adult stud ies). Mean pure-tone thresholds in the 1,000- to 8,000-Hz frequency range a re up to 20 dB worse than ABR thresholds, which is opposite to findings in normally-hearing subjects. Thus, with an increasing degree of sensorineural hearing impairment, pure-tone thresholds increase at a significantly highe r rate than ABR thresholds. The observation is explained in terms Df reduce d temporal integration in cochlear hearing loss. ABR thresholds worse than 80 dB nHL are demonstrated to have very limited predictive value with respe ct to the amount of residual hearing, not only in the low- but also in the high-frequency range. The presence of otitis media during ABR testing is sh own to make estimation errors increase to more than 25 dB (SD).