Brainstem Auditory Evoked Response Recorded Using Maximum Length Sequences in Term Neonates

Abstract

Brainstem auditory evoked response (BAER) was studied in term neonates using maximum length sequences (MLS), which allows presentation of acoustic stimuli at much higher rate than possible with conventional averaging technique. The response waveforms, especially for waves III and V, were well defined at the click rates of 91–455/s. Wave latencies and interpeak intervals at various click rates were all significantly longer and wave V amplitude was smaller in the neonates than in the adults. As click rate was increased, wave latencies increased and amplitudes progressively reduced. The slopes of wave latency-rate functions were progressively steeper for the later waves. The slopes of both III–V and I–V interval-rate functions were significantly steeper in the neonates than in the adults, indicating greater rate-dependent changes in the central components of the neonatal MLS BAER. These rate-dependent changes in the neonatal MLS BAER are generally similar to those in neonatal conventional BAER, although there are some differences. The results indicate that the neonatal brainstem can process rapid acoustic stimulation up to 455/s, although this ability remains immature.

Time Course of Brainstem Pathophysiology during First Month in Term Infants after Perinatal Asphyxia, Revealed by MLS BAER Latencies and Intervals

“…The normal control subjects were 38 healthy newborn infants (18 (23,24). Briefly, the subjects lay supine in their crib.…”

“…Our recent studies indicate that to improve the detection of neuropathology the repetition rate of stimuli should be high enough to effectively stress the large number of neurons along the brainstem auditory pathway (18,21,22). However, conventional averaging technique imposes a rate limit of approximately 100/s, which restricts the ability of the method of increasing click rate to improve early detection of neural impairment (23,24). We have recently studied a relatively new technique, the MLS BAER, in infants of various ages (23)(24)(25).…”

“…However, conventional averaging technique imposes a rate limit of approximately 100/s, which restricts the ability of the method of increasing click rate to improve early detection of neural impairment (23,24). We have recently studied a relatively new technique, the MLS BAER, in infants of various ages (23)(24)(25). The major advantage of this technique is that it can present acoustic stimuli at much higher rates (up to 1000/s or even higher) than is possible using conventional BAER (23)(24)(25)(26)(27)(28)(29).…”

“…We have recently studied a relatively new technique, the MLS BAER, in infants of various ages (23)(24)(25). The major advantage of this technique is that it can present acoustic stimuli at much higher rates (up to 1000/s or even higher) than is possible using conventional BAER (23)(24)(25)(26)(27)(28)(29). The higher rates provide a much greater temporal or physiologic challenge to brainstem auditory neurons, potentially enhancing the detection of neuropathology.…”

Maximum Length Sequence Brainstem Auditory Evoked Responses in Term Neonates Who Have Perinatal Hypoxia-Ischemia

“…This relatively new technique uses patterned stimulus presentation rather than the uniformly spaced stimuli used in conventional BAER. The nature of the stimulus and newly developed processing technique make it unnecessary to wait for the response of each pulse to be completed before applying a new pulse, thus allowing the pulses to be delivered at rates of up to 1,000/s or even higher (15)(16)(17)(18)(19)(20)(21)(22). Because the patterned sequences of stimuli are generated by the averaging computer, this information is then used to perform online deconvolution (separation, alignment, and averaging) of overlapping individual responses.…”