Maturation of the Contralaterally Recorded Auditory Brain Stem Response

Abstract

lpsilaterally and contralaterally recorded auditory brain stem responses to 80 dB nHL clicks were recorded from 37 infants, aged 2 weeks to 20 mo and from six adults, all with normal auditory function. With increasing age, contralateral waves A, B, C, and D and ipsilateral waves 111 and V decreased in latency, with the contralateral morphology more closely resembling the ipsilateral morphology as age increased, especially after the age of 9 mo. The mean latencies and their change with age for waves A and B resembled those of ipsilateral waves 111 and Ill', respectively; both waves C and D demonstrated similarities with wave V. Large waveform changes were seen with maturation in the latency region of contralateral waves C and D. In 42 of 43 subjects, wave V latency occurred after wave C and before wave D. Peak to peak amplitudes of contralateral waves A-B and D-E' increased with age, but were smaller than those of ipsilateral 1'-111 and V-V', respectively. The smaller contralateral responses make their use for threshold estimation problematic, especially before the age of 9 months. The contralateral response, however, may help to select wave V in ambiguous cases, and to determine response laterality (Ear Hear 12 3: 167-173).

Normal Ipsilateral/Contralateral Asymmetries in Infant Multiple Auditory Steady-State Responses to Air- and Bone-Conduction Stimuli

“…This is the first study that has investigated ipsilateral/contralateral asymmetries in ASSRs elicited by air-and bone-conduction stimuli in infants and adults. Clearly, ASSRs recorded in the EEG channels ipsilateral and contralateral to air-and boneconduction stimuli in infants are not the same as those in adults, a pattern similar to previously reported results for ABRs to air- (Edwards, et al, 1985;Stapells & Mosseri, 1991) and bone-conduction stimuli (Foxe & Stapells, 1993;Stapells & Ruben, 1989;Stuart, et al, 1996).…”

“…In contrast, adults have more similar wave V amplitudes and latencies in the two channels. These latency and amplitude asymmetries in infants are present at all intensity levels and persist until at least 1 to 2 yr of age (Stapells & Mosseri, 1991). The ipsilateral/contralateral asymmetries, which relate both to developmental changes in skull structure and to neurophysi-ology, may be used to provide valuable diagnostic information when assessing bone-conduction hearing in infants by identifying the cochlea that is responding to the stimulus (Foxe & Stapells, 1993;Stapells, 2000;Stapells & Ruben, 1989).…”

“…A number of studies using monaural air-conducted click stimuli have shown that the morphology of the ABR waveform in the contralateral EEG channel differs from that in the ipsilateral EEG channel (Edwards, et al, 1985;Furune, et al, 1985;Stapells & Mosseri, 1991). In young infants, the ABR waveform in the ipsilateral EEG channel has recognizable waves I, III and V; yet, in the contralateral EEG channel, the peaks in the ABR waveform differ in polarity, amplitude and latency to the degree that a new labeling scheme for the contralateral response using the letters A through E was proposed (Edwards, et al, 1985).…”

“…In young infants, the ABR waveform in the ipsilateral EEG channel has recognizable waves I, III and V; yet, in the contralateral EEG channel, the peaks in the ABR waveform differ in polarity, amplitude and latency to the degree that a new labeling scheme for the contralateral response using the letters A through E was proposed (Edwards, et al, 1985). Stapells and Mosseri (1991) reported that the peak-to-peak amplitudes of A-B and D-E' in the contralateral EEG channel are smaller than the I'-III and V-V' in the ipsilateral channel for infants at least up to 18 mo of age which is consistent with the results reported earlier for neonates by Edwards et al (1985). Edwards et al also reported that only 35% of neonates had contralateral responses to 30 dB nHL air-conducted clicks, which is similar to the percentage of infants that had contralateral ASSRs to air-conduction stimuli in the present study.…”

“…In contrast, adults have more similar wave V amplitudes and latencies in the two channels. These latency and amplitude asymmetries in infants are present at all intensity levels and persist until at least 1 to 2 yr of age (Stapells & Mosseri, 1991). The ipsilateral/contralateral asymmetries, which relate both to developmental changes in skull structure and to neurophysi-…”