Maximum length sequence brainstem auditory evoked responses in term neonates who have perinatal hypoxia-ischemia

Maximum length sequence brainstem auditory evoked response (BAER) was studied within the first week after birth in 28 term neonates who had perinatal hypoxia-ischemia, or asphyxia. In the BAER recorded using conventional averaging techniques (click rate 21/s), the only abnormality was a slight increase in III-V interval, in addition to an increase in wave latencies when including those who had an elevated threshold (t test, all p < 0.05). In the maximum length sequence BAER, however, both the m-v and I-V intervals in the asphyxiated infants were significantly increased at all the 91/s, 227/s, 455/s, and particularly 910/s click rates (p < 0.05-0.001). The I-III interval was also increased significantly at 455/s and 910/s click rates (both p < 0.05). Wave V amplitude was significantly reduced at all the click rates used (ANOVA, p < 0,05-0.001), particularly at 910/s, which sometimes was the only abnormality indicative of brain damage. Both the amplitude ratios V/I and V/III were significantly decreased at 455/s and 910/s click rates (p < 0.01 or 0.001). A general trend was that BAER abnormalities after hypoxia-ischemia became more prominent as click rate was increased. Significant abnormalities occurred mainly at very high click rates (455/s and 910/s), which can be achieved using the maximum length sequence technique but not by using conventional averaging techniques. Thus, this technique, which can be used at the cribside, appears to be a better method for the early detection of brain damage after hypoxia-ischemia than using conventional averaging techniques, enhancing the diagnostic value of the BAER.