Abstract 2024 Poster Session II, Sunday, 5/2 (poster 220)

Maximum length sequence brainstem auditory evoked response (MLS BAER) allows presentation of stimuli at much higher rates than is possible using conventional averaging techniques. Thus, stimuli presented using the MLS technique can provide a much greater physiological challenge to brainstem auditory neurones and potentially enhance the detection of neuropathology. We have recently studied this relatively new technique in newborn infants with a gestational age (GA) of 23-42 weeks to evaluate the feasibility and validity of the MLS BAER in detecting auditory impairment in high risk infants.

Methods: The MLS BAER was recorded at the click rates of 90, 227, 455 and 910/sec in 60 neonates with various perinatal problems. Conventional BAER was also recorded a20, 50 and 90/sec clicks for comparison. The results of these infants were compared with those of the infants without problems (n = 32) at comparable postnatal ages (CA). RESULTS: A significant increase in BAER threshold (≥ 50 dB nHL) was found in 5 of the 60 infants. Of the remaining 55 infants, 21 (38.2%) showed abnormalities in central components of the MLS BAER, including significantly prolonged III-V and I-V interpeak intervals and reduced amplitude of wave V, which occurred mainly at very high click rates (455 and 910/sec). The abnormalities were predominantly seen in the infants who were born with a GA ≤ 32 weeks and/or a birthweight < 1,500g and had asphyxia, severe hyaline membrane disease and severe intra-uterine growth retardation. The I-V and III-V intervals in the infants with perinatal problems differed significantly from those of the age-matched infants without problems at 455 and 910/sec clicks (p < 0.05-0.01). By contrast, abnormalities in conventional BAER were seen in only 8 of the 55 infants (14.5%). During the postnatal period, the MLS BAER abnormalities tended to normalise with the recovery of perinatal problems in most of the infants but persisted longer in a few. In some cases the III-V and I-V intervals were significantly shortened at 910/sec clicks. Conclusion: (1) MLS BAER abnormalities occurred mainly in the infants born very prematurely and/or with very low birthweight who had major perinatal problems that may either directly or indirectly cause hypoxic and/or ischaemic damage to the brain. (2) BAER abnormalities were often revealed only at very fast stimulus rates, particularly 910/sec, that can be achieved by the MLS technique but cannot by conventional averaging techniques. Thus, the MLS BAER, that can be used at the cot-side, provides a potentially sensitive method to detect early or subtle auditory impairment that may not be revealed by conventional techniques, enhancing the diagnostic value of the BAER. (Supported by R&D, Anglia and Oxford RHA, UK).