Electrophysiological and behavioral methods in early detection of hearing impairment

Recent advances in neonatal life-support systems have contributed to the survival of high-risk newborns. However, protection of the auditory system and the prevention of sequelae is still paramount in neonatal neurology. The aim of this study was to compare auditory-evoked responses with a toy test and acoustic reflex in the early detection of hearing loss in infants.

Three groups were studied. The first was composed of infants showing less than a 30 dB biaural threshold in the neurophysiological test. The second group was made up of infants showing peripheral alterations on one side or both ears. The third group was comprised of infants who showed no responses at 95 dB HL in both ears after neurophysiological testing. The neurophysiological test, toy test, and acoustic reflex were performed on the same day, with masked results given to each investigator. Sensitivity and specificity for each toy test and acoustic reflex were calculated afterward.

Forty-five controls, 44 peripheral alterations, and 8 non-response infants were studied. Most patients studied were born prior to the 37(th) week of gestation with a birthweight of less than 2,250 g, received required administration of potential ototoxic drugs and mechanical ventilation, and showed hyperbilirubinemia and hypoxia. Sensitivity for each toy was as follows: drum 0.54; wooden rattle 1.0, and metallic ratle 0.88. Specificity was 0.95, 1.0, and 1.0, respectively. Acoustic reflex sensitivity was 0.38 and specificity was 0.97.

Results suggest that the wooden and the metallic rattles of the toy test can be useful tools in the study of hearing in the high-risk infant and deserve more attention in future studies.