Auditory‐evoked responses in normal, brain‐damaged, and deaf infants

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Abstract
Auditory- and visual-evoked responses, recorded from the scalp eeg with the aid of a summating computer, were studied in 61 infants aged 1 day to 3 years. They were tested on 80 occasions during sleep. Chlorpromazine was a suitable sedative for this test. Procedural improvements which were introduced to expedite clinical testing were described. All infants had evoked responses to sound, with the exception of 2 infants whose eeg was isoelectric and who also failed to have evoked responses to light Latencies of waves P2 and N2 recorded at the vertex were measured and variable. During active sleep, responses were smaller and the proportion of false-negative runs somewhat larger than during quiet sleep. In 18 normal infants, responses were present in 91% of runs with tone pips or clicks above 80 decibels re: 0.0002 dynes per square centimeter and in 77% of runs between 50 and 79 decibels. Among 19 infants with brain damage and nonisoelectric eeg''s, 11 had normal and 2 had elevated thresholds. Data were incomplete in the others. In 1 infant with asymmetrical damage, responses disappeared at higher intensity levels from the electrode overlying the more damaged of his hemispheres. Brain damage apparently did not affect threshold for the response unless it was very severe. Five otherwise normal infants suspected of hearing losses had elevated thresholds, as did all but 2 of 17 infants severely affected by intra-uterine rubella. By this method, residual hearing was detected and measured in 8 infants with brain damage and in 11 infants with rubella, all of whom gave inconsistent or no behavioral response to sound and all of whom were afflicted with additional handicaps such as psychomotor retardation and visual loss. Retest in 8 infants while they wore hearing aids established effective amplification in 7.

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