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The maturation of the central auditory conduction in preterm infants until three months post term. III. The middle
Insights
This study shows that middle latency auditory evoked responses (MLRs) in premature infants mature significantly with conceptional age (CA). Auditory pathway development in preterm infants is reflected in these brain responses.
Area of Science:
- Neuroscience
- Developmental Biology
- Audiology
Background:
- Premature infants often experience auditory pathway developmental challenges.
- Understanding auditory evoked responses is crucial for assessing neurological development in preterm infants.
Purpose of the Study:
- To investigate the maturation of middle latency auditory evoked responses (MLRs) in premature infants.
- To analyze MLR components (PO, Na, Pa) and their age dependency.
- To explore topographic and vigilance state influences on MLRs.
Main Methods:
- Recorded serial middle latency auditory evoked responses (MLRs) in 64 premature infants up to 52 weeks conceptional age (CA).
- Analyzed MLR components (PO, Na, Pa) and interpeak latency difference (IPLD) Na-PO.
- Assessed detectability rates, latency, amplitude, and topographic differences.
Main Results:
- PO and Na components were detectable in 80-90% of infants by 30 weeks CA; Pa detection peaked at 60% by 52 weeks CA.
- MLR component latencies showed strong age dependency, with topographic differences observed between ipsilateral and contralateral stimulation.
- Vigilance state influenced MLRs around 32 and 52 weeks CA, with amplitudes being particularly sensitive at 52 weeks CA.
Conclusions:
- MLR development in premature infants is strongly age-dependent, reflecting the maturation of the auditory pathway.
- Bilateral generation and early subcortical functioning contribute to the observed MLR patterns.
- MLRs serve as a valuable tool for monitoring auditory and neurological development in preterm infants.
Abstract:
Middle latency auditory evoked responses (MLRs) were recorded in 64 premature infants; serially in 54 of them. The last recording sessions occurred at 50-52 weeks conceptional age (CA), defined as the gestational age (GA) added to the chronological age. The MLRs were analyzed for the components PO, Na and Pa, and the interpeak latency difference (IPLD) Na-PO. The detectability rate of PO and Na reached 80-90% at about 30 weeks CA. Pa reached the highest rate of about 60% at 52 weeks CA. The degree of prematurity did not result in clear differences with respect to the parameter values. Also, the side of stimulation did not influence the MLR parameter values. The latency values of the MLR components are strongly age dependent. Topographic differences were found between the sides ipsi- and contralateral to stimulation. They are, however, different for PO, Na and Pa. The influence of the state of vigilance on the parameter values could generally only be established at CA levels of about 32 and 52 weeks CA. The amplitude values at 52 weeks CA are especially sensitive for sleep or awake state. The particular pattern of age dependency of the different components and their topographic differences are consistent with a differential generation of bilateral nature. The early appearance of the response supports the generation of an early functioning subcortical structure in the auditory pathway.