This study examined whether high presentation rates of clicks while recording brainstem auditory evoked responses (BAER) can improve the detection of central auditory impairment in asphyxiated neonates using the BAER. The BAER was analysed at different presentation rates of clicks within the first week after birth in 38 term neonates who suffered perinatal asphyxia. At the routinely used 21 s−1 clicks all BAER wave latencies increased significantly (ANOVA, p < 0.05‐0.01). After excluding five neonates who had a significantly elevated BAER threshold, only wave V latency increased slightly (p < 0.05). The interpeak intervals of I–V and III–V also increased slightly (both p < 0.05). Similar results were found at 51 s−1 clicks. As the clicks were increased to 91 s−1, the III–V interval increased more significantly (p < 0.01) and the III–V/I–III interval ratio also increased significantly (p < 0.01). In particular, wave V amplitude reduced more significantly than that in normal term controls (p < 0.01). Compared with values in the controls, wave V amplitude reduced by 4.5%, 12.2% and 24.7% at 21, 51 and 91 s−1 clicks, respectively. Conclusion: Although a moderate increase in the rate (e.g. 51 s−1) while recording the BAER did not improve the detection of hypoxic‐ischaemic auditory impairment, a significant increase (e.g. 91 s−1) did, which mainly indicates an abnormal reduction in wave V amplitude.

Seventy preterm babies who were born with a birthweight <1500 g were studied with brainstem auditory evoked responses (BAER) at 37‐42 wk of postconceptional age. The data were compared with those of normal term neonates to determine the prevalence of hearing impairment in preterm very low birthweight (VLBW) babies when they reached term. The BAER was recorded with click stimuli at 21 s−1. Wave I and V latencies increased significantly (ANOVA p < 0.01 and 0.001). I‐V and III‐V intervals also increased significantly (p < 0.05 and 0.001). Wave V amplitude and V/I amplitude ratio did not differ significantly from those in the normal term controls. Ten of the 70 VLBW babies had a significant elevation in BAER threshold (>30 dB normal hearing level). Eleven had an increase in I‐V interval (>2.5 SD above the mean in the normal controls) and one had a decrease in V/I amplitude ratio (<0.45). These results suggest that 14% (10/70) of the VLBW babies had a peripheral hearing impairment and 17% (12/70) a central impairment. Three babies had both an increase in I‐V interval and an elevation in BAER threshold, suggesting that 4% (3/70) had both peripheral and central impairments. Thus, the total prevalence of hearing impairment was 27% (19/70). Conclusion: About one in four preterm VLBW babies has peripheral and/or central hearing impairment at term. VLBW and its associated unfavourable perinatal factors predispose the babies to hearing impairment.

Aim: To clarify further the influence of intrauterine growth retardation (IUGR) on early neural development. Methods: In 30 small‐for‐gestational age (SGA) preterm infants at term, brainstem auditory‐evoked responses (BAERs) were recorded with clicks of different repetition rates. All infants had a birthweight >3rd centile, without any other major perinatal complications. Results: Compared with the BAER in 36 appropriate‐for‐gestational age (AGA) term infants, the preterm SGA infants did not show any abnormalities at 21 s−1 clicks, except for a slight increase in wave III amplitude. At 51 s−1 clicks, there was an increase in III–V/I–III interval ratio (ANOVA p < 0.05). At 91 s−1, the I–III interval shortened, whereas the III–V interval and III–V/I–III interval ratio increased (all p < 0.05). Wave V amplitude tended to increase slightly at all repetition rates of clicks used, although this increase did not reach statistical significance. The III–V interval and III–V/I–III interval ratio in the preterm SGA infants at different click rates correlated inversely with occipitofrontal head circumference at the time of testing, i.e. the smaller the head the longer the III‐V interval (all p < 0.01). Wave III amplitude at 21 s−1 also correlated inversely with head circumference (p < 0.01), suggesting that the slight increase in this amplitude in the preterm SGA infants is related to their relatively small head size. Conclusion: There were no major abnormalities in the BAER up to 91 s−1 clicks at term in preterm SGA infants. The slight increase in III–V interval at high‐rate stimulation suggests a subtle degree of central neural dysfunction, which is associated with small head size following IUGR.