Auditory brainstem responses in normal hearing ears

It is essential to know the expected auditory brainstem response latencies of a normal hearing population to utilise this procedure as a diagnostic tool. Absolute wave latencies of the auditory brainstem responses were recorded on 50 normal hearing subjects, aged 3 months to 56 years using a standard sound pressure level of 115 dB alternate clicks. The recordings were examined for differences in latencies between the age groups, sexes and the left and right ears. The results showed that the absolute latencies of subjects aged 2 years and above were the same and no significant differences were obtained between the left and right ears. The infants showed longer latencies. The brainstem transmission time values were calculated as from Wave NI-NIII, Wave NI-NV and Wave NIII-NV. A comparison of the brainstem transmission times between the left and right ears of each individual subject showed that in all cases the differences did not exceed more than 0.2 msec. A value of more than 0.2 msec between the two ears of an individual may be of diagnostic importance. In comparing the male and female brainstem transmission times, there was a significant difference statistically. Another value to use was the Wave PV, which is the most prominent and stable peak. The results showed that the Wave PV latency progressively shortens during infancy to attain the adult value somewhere between 18 and 24 months.