Brainstem auditory evoked responses from birth to adulthood: development of wave amplitude.

Brainstem auditory evoked response (BAER) was recorded in children from birth to 6 years and adults to study the development of wave amplitude. The amplitudes of all BAER waves increased with age, the greatest changes occurring during early infancy. Adult values were reached at 6 months of age for wave I and 2 years for wave V. The two waves continued to increase above the adult values until the highest amplitude value was reached at 3 years for wave I and 5 years for wave V. Subsequently, the amplitudes decreased towards the values in adults. The V/I amplitude ratio, which was slightly than the adult value shortly after birth, decreased during the first year of life and reached the minimum value between 1 and 4 years. Thereafter, it increased towards the adult value. Throughout the maturational stages the ratio was smaller than in adults. The amplitude of wave V was relatively stable and its variation was much smaller than those of wave I and V/I amplitude ratio. Lower normative limits of these amplitude measures were given to provide a reference baseline for further study under the similar experimental conditions. We suggest that, in light of age-related differences of the V/I ratio, the normative criteria for the amplitude ratio should be established in relation to age. The amplitude of wave V is recommended to be useful in some clinical situations.