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Visual evoked potentials in preterm infants during the first hours of life
O Pryds1, G Greisen, W Trojaborg
1Department of Neonatology, State University Hospital of Copenhagen, Denmark.
Insights
Visual evoked potentials (VEPs) in preterm infants show that latency decreases with increasing core temperature and is related to gestational age. VEPs can monitor cerebral function in neonates.
Area of Science:
- Neonatal neurology
- Neurophysiology
- Developmental neuroscience
Background:
- Preterm infants exhibit immature visual pathways.
- Assessing cerebral function in neonates is crucial for early intervention.
- Visual evoked potentials (VEPs) offer a non-invasive method to evaluate visual pathway integrity.
Purpose of the Study:
- To investigate the characteristics of flash-evoked VEPs in preterm infants.
- To determine the influence of physiological factors (gestational age, core temperature) on VEPs.
- To explore the utility of VEPs for monitoring cerebral function in this population.
Main Methods:
- VEPs were recorded in 33 preterm infants (27-33 weeks gestational age) within 12 hours of birth.
- VEP latency and amplitude were analyzed, considering core temperature and gestational age.
- Factors like flash intensity, background illumination, subependymal hemorrhages, and hypoxia were assessed for their impact on VEPs.
Main Results:
- A visual response was elicited in all infants.
- VEP latency decreased with increasing core temperature (6 msec/°C) and was inversely related to gestational age.
- VEP amplitude was also inversely related to gestational age; neither was affected by flash intensity or background illumination within tested ranges.
- Minor subependymal hemorrhages did not affect VEPs, but hypoxia severely attenuated them.
Conclusions:
- VEP latency and amplitude are influenced by core temperature and gestational age in preterm infants.
- VEPs are robust to moderate changes in visual stimulation parameters.
- VEPs show potential as a tool for assessing cerebral function in preterm neonates, especially when core temperature is considered.
Abstract:
Flash evoked cortical potentials (VEPs) were studied in 33 preterm infants with gestational ages from 27 to 33 weeks. During the first 12 h after birth a visual response was evoked in all infants. Better estimates of the VEP latency and amplitude were obtained by using the values of 3 VEPs recorded at 30 sec intervals. The VEP latency decreased during the first hours of life, which was accounted for by an increase in core temperature; the latency decreased 6 msec/degrees C increase. Changes in amplitude were less influenced by changes in temperature. Both VEP latency and amplitude were inversely related to gestational age, but there was no association between head circumference and latency. The flash intensity could be reduced from 155 cd to 39 cd without any effect on VEP latency or amplitude. Similarly, a variation of background illumination below 200 lux did not cause VEP changes. The VEP was not affected by development of minor subependymal haemorrhages but it was severely attenuated during a short episode of hypoxia. It is suggested that when taking core temperature into account the VEP can be used to determine changes in the cerebral function in preterm infants.