Abstract
An early auditory evoked response with latency of 5 to 8 msec (brain stem response, BSR) was recorded from the human scalp, and the consistency and the reliability of this response were studied to evaluate its applicability as the objective method for assessing hearing of infants and children.
Method Subjects were five young children aged from 2 to 6 years with normal hearing. The responses were recorded during sleep induced by oral sedative. Active and reference electrodes were atta-ched to the vertex and a earlobe. Ground electrode was placed on the skin between the eye-brows. The responses were amplified and averaged by a medical computer, whose analysis time was set at 25 msec. As a rule, 2000 signals were averaged in a test run and the averaged respo-nses were recorded with a X-Y recorder.
Click stimuli were given through a loudspeaker at intervals of 50 msec. The test was perfo-rmed at the intensity levels of 10, 20, 30 and 40 dB above mean subjective thresholds of normal adults (HL). A series of 10 averaged traces were obtained for each stimulus intensity and 10 ad-ditional traces were recorded without stimulation. Thus 50 samples were obtained from each subject.Then the presence or absence of the response in a total of 250 samples was examined by 3 tra-ined scorers using forced choice method.
Results 1. Average percentages of positive responses were 45.3, 92.0, 99.3 and 100% at the inten-sity levels of 10, 20, 30 and 40 dB HL respectively.
2. False positive was found in 7.3 % of the traces without stimulation.
3. Agreement of judgement between 3 scorers was obtained in 68 % (10 dB), 88 % (20 dB), 98 % (30 dB), 100% (4o dB) and 90 % (no stimulus) of the samples tested.
4. As compared with the auditory slow vertex response, the brain stem response appeared more constantly, and reliably.
