How to Obtain Reliable Visual Event-related Potentials in Newborns

Summary

Several important points for obtaining high-quality reliable visual evoked potentials (VEPs) in newborns while minimizing variability and the risk of misleading prognoses are presented.

Abstract

The present study discusses the characteristics of visual event-related potentials (VEPs) and outlines methodological steps for obtaining reliable measurements in newborns. Obtaining high-quality, reliable VEPs is crucial for the early detection of abnormal development of the central nervous system in at-risk newborns, and for implementing successful early interventions. Recommendations are based on a previous study which showed that when post-conceptional age, polysomnography-identified sleep stages, and light-emitting diodes (LEDs) googles as the luminous source are controlled, no more than 4 repetitions of VEP averages are required to obtain replicable recordings, variability decreases, and reliable VEPs can be obtained. By controlling for these sources of variability and using statistical analyses, we were able to clearly and reliably identify the amplitude and latency of three main components (NII, PII and NIII) present in 100% of newborns (n = 20) during active sleep. Recording VEPs during awake states, quiet sleep and transitional sleep is not recommended because VEP morphology may differ significantly from one average to the next, leading to the risk of misleading clinical prognoses. Moreover, it is easier to obtain VEPs during active sleep because this state can be clearly and reliably identified at this stage of development, sleep cycles are short enough to allow measurements to be taken in a reasonable time, and the method does not require new o expensive equipment.

Introduction

Early detection of abnormal development of the central nervous system in at-risk newborns is crucial for successful early interventions^1,2. Visual event-related potentials (VEPs) provide a useful means of evaluating visual cortical status because they do not require patient cooperation, which is not possible in the first month of life, are objective, and are sensitive to structural and functional brain damage^3,4.

Though, some studies of newborns have shown that normal visual-evoked responses indicate adequate neural maturati....

Protocol

1. Preparation of the Newborns

NOTE: The procedure followed is innocuous and painless, so there are no counter-indications for evaluating full-term and preterm newborns, once they are clinically stable.

1. Ensure two and half hour fasting and wakefulness before beginning the study, in neonates older than 40 weeks of postconceptional age.
2. Make sure that the baby's head be washed with neutral soap the day before the study. Thus, his/her hair will be clean .......

Discussion

Three components of visual-evoked responses (NII, PII and NIII) were characterized in healthy, full-term newborns while doing stimulation with LED googles, and recorded during polygraphically-identified sleep states. The VEP morphology observed is consistent with previous results reported for fewer neonates^11,15. The characterization of VEP responses was achieved by recording 20 healthy, full-term newborns at similar post-conceptional age¹⁶

Materials

Name	Company	Catalog Number	Comments
Digital Electroencephalograph	Neuronic Mexicana, SA	Medicid 3E	Sleep electroencephalogram record
Evoked Potentials equipment	Neuronic Mexicana, SA	Neuronic PE (N_N-SW-2.0)	Visual evoked potentials record
Nuprep Gel	WEAVER and Company		Skin preparing abrasive gel (114 g)
Ten20 Conductive Paste	WEAVER and Company		Neurodiagnostic electrode paste (228 g)
Tubular elastic mesh bandage	Le Roy		Fixation of cranial surface electrodes, Size 4 or Small