Auditory Neural Responses to Click Stimuli of Different Rates in the Brainstem of Very Preterm Babies at Term

Abstract

Auditory neural responses to acoustic stimuli of different rates were studied by analyzing changes in brainstem auditory evoked responses (BAER) with increasing repetition rate of clicks, or rate-dependent changes, in 62 very preterm babies (gestation 24 -32 wk). None had perinatal asphyxia or major complications at the time of testing (37-42 wk postconceptional age) to exclude their possible effects on the recorded BAER. As the rate of clicks was increased from 21/s to 51/s and 91/s, I-V interpeak interval in these babies increased similarly to that in normal term neonates. The rate-dependent change decreased significantly in I-III interval, but increased significantly in III-V intervals and III-V/ I-III interval ratio (all p Ͻ 0.01). At all three rates of clicks, the I-V interval, the most commonly used BAER variable, tended to increase slightly but did not differ significantly from the term neonates. The I-III interval decreased significantly at higher click rates (ANOVA p Ͻ 0.05 at 51/s and Ͻ 0.001 at 91/s), whereas the III-V interval and III-V/I-III interval ratio increased significantly at all 21/s, 51/s, and particularly 91/s (p Ͻ 0.01-0.001). No abnormalities were found in wave V amplitude at any rates. These results suggest that very preterm babies have an advanced peripheral development of the brainstem auditory pathway but a retarded central development or central impairment. A nearly normal I-V interval does not exclude a possible abnormality in its subcomponents (I-III and III-V intervals). In babies who have a normal BAER at a conventionally used low rate of clicks, we cannot exclude an abnormal BAER at higher rates. Babies who are born very preterm account for a large proportion of perinatal mortality and are at high risk of neurodevelopmental deficits (1-5). Many of the survivors have long-term neurologic disorders or behavior problems, e.g. minimal brain damage and learning disabilities, and visual and hearing deficits. Those who have sensorineural hearing loss develop more neurologic complications than control infants (6). However, there are still controversies regarding early neural development in these babies. Some investigators reported a delay in development (7-9), whereas others found no apparent abnormality (10, 11). Better understanding of the early development and neurophysiology underlying later disability is important for improving the management of these babies.BAERs represent the electrophysiologic activity of a large number of auditory neurons in the brainstem after transient acoustic stimulation. The responses have been widely used to study auditory function and its development in babies (12)(13)(14)(15)(16)(17)(18). Although most of the previous BAER studies in preterm babies reported no significant abnormalities (12, 18), others reported an increase in BAER wave latencies and intervals, suggesting retarded development (16). To date, none of the previous reports were concentrated on the study of BAER central components in very preterm babies.The neonatal BAER is significantly aff...

Relative Maturation of Peripheral and Central Regions of the Human Brainstem From Preterm to Term and the Influence of Preterm Birth

“…The procedures of BAER recording and analysis were the same as previous described (11,16). Briefly, three gold-plated disk electrodes were placed at the middle forehead (ϩ), the ipsilateral (left) earlobe (Ϫ), and the contralateral (right) earlobe (ground).…”

“…Maturation of the BAER is associated with myelination of axons, formation of central synaptic connections, and axonal diameter and has been found to correlate with maturation of the brainstem, as well as the auditory pathway (8 -10). During early life, the BAER undergoes tremendous maturational changes, characterized by a shortening of wave latencies and an increase in wave amplitudes of the response (11)(12)(13)(14). Furthermore, a shortening of the intervals between BAER wave peaks (i.e., interpeak intervals) with increasing age has been well documented.…”

Brainstem Auditory Function at Term in Preterm Babies With and Without Perinatal Complications

“…To improve the detection of neuropathology that affects the auditory brainstem, we used the method of increasing the rate of clicks while recording conventional BAER (9,19,20). The results show that this method can improve the detection to a certain degree.…”

“…As an objective test to study functional integrity of the auditory brainstem, the BAER has been used to study functional development of the human auditory system and detect auditory impairment and neuropathology that affects the brainstem auditory pathway (7)(8)(9)(10)(11)(12). Nevertheless, the BAER, recorded using conventional averaging technique, has a relatively high false-negative rate.…”

The use of QSD (q-sequence deconvolution) to recover superposed, transient evoked-responses

“…For example, Hecox et al (1981) stated that for pediatric applications of the auditory brainstem response (ABR), "…increasing rate of stimulation facilitates the identification of [ABR] abnormalities". As late as 2002, the use of high-rate stimuli has been strongly advocated for the ABR when evaluating preterm infants (Jiang et al, 2002). (see the Discussion and Table 1 for additional, extensive evidence for the known value of using a high stimulus repetition-rate to detect brainstem disorders.…”