Elsevier

Brain and Development

Volume 19, Issue 8, December 1997, Pages 547-551
Brain and Development

Original article
Stepwise decrease in VEP latencies and the process of myelination in the human visual pathway

https://doi.org/10.1016/S0387-7604(97)00076-4Get rights and content

Abstract

To assess the progress in myelination in the developing human brain, a prospective longitudinal study of flash visual evoked potentials (VEPs) was performed in 22 healthy preterm infants with the same gestational age at birth (between 30 weeks 0 day and 31 weeks 0 day). The individual curves of the changes in the N1a peak latency (the early peak of the N1 wave) decrease not linearly but in a stepwise pattern in the preterm period. Twenty-one infants out of the 22 have one or more `acceleration week(s)' in which the latency decreases at a rate of more than 6 ms per week. These stepwise decreases in the latency may reflect a synchronized progress in myelination in several parts of the visual pathway. A detailed analysis of the `acceleration weeks' in relation to postmenstrual age (PMA) indicates that they most prominently occur at 37 weeks PMA. At 37 weeks an initiation of myelination in the optic radiation has been demonstrated in post-mortem studies. We propose that a longitudinal follow-up study of VEPs can be accepted as a functional in vivo evaluation of myelination in the developing human brain.

Introduction

Myelination is a most fascinating developmental process in the developing brain. One type of glial cell, the oligodendrocyte, is mainly responsible for this process. Oligodendrocytes produce two unique hydrophobic proteins, myelin basic protein (MBP) and proteolipid protein. They wrap axons tightly with these special proteins and lipids. From post-mortem anatomical studies using an immunostaining method for MBP 1, 2and from electron microscopy studies [3], direct information about myelination in the developing human brain has been obtained. Recently, magnetic resonance imaging (MRI) has been introduced in preterm infants 4, 5, 6as well as in term neonates 7, 8to assess the progress in myelination in vivo. MRI detects the accumulation of the substances which are necessary for the components of the myelin sheath, and it also detects a decrease of water content 4, 5, 8. There is a time lag between the initiation of myelination and its detectability using T1-weighted images [9].

For the functional assessment of myelination electroneurophysiological techniques seem most suitable. Longitudinal studies of brainstem auditory evoked potentials and somatosensory evoked potentials in preterm infants have been reported. These studies demonstrated a continuous shortening of the peak latencies with maturation 10, 11, 12. Visual information travels a long distance within the central nervous system. This fact may enable us to obtain indirect but functional evidence of the progress in myelination by the study of the changes in the VEP peak latencies.

Using the N1 peak denominations that we proposed recently [13], we observed a specific timing in the rapid decreases of the latencies. These findings may correlate with the progress of myelination in the visual pathway.

Section snippets

Methods

Twenty-two healthy preterm infants of appropriate birth weights for gestational age (GA), who were born at the GAs of 30 weeks 0 day to 31 weeks 0 day, were included in this prospective study. The mean birth weight was 1400±201 g and mean GA was 30.5±0.4 weeks. The GA was assessed by menstrual dates, ultrasound evaluation and postnatal clinical assessment, and doubtful cases were excluded. Infants with neurological problems or anomalies, perinatal infectious diseases and other severe systemic

Results

Since 21 infants out of the 22 had both some `stable weeks' and one or more `acceleration week(s)', the N1a latency decreased not linearly but in a stepwise pattern. Two illustrative examples are presented in Fig. 1Fig. 2. Only one infant (case no. 17) failed to show any `acceleration weeks' but she had 3 consecutive weeks between 33 and 36 weeks PMA in which the latency decreased at 4 ms per week. No infant presented with increases in the latency of 6 ms per week or more.

There were total 48

Discussion

In a previous study from our department [13], it was demonstrated that VEP can reliably be recorded and analyzed in the preterm period. In that study a stepwise decrease in the N1a latencies was observed (Fig. 1, Fig. 2). We speculate that the progressive rapid decreases in the latency may reflect phases with synchronized increases in the myelination of the visual pathway. The timing of the progress in the myelination in different parts of the pathway may thus be detected in vivo using a

Acknowledgements

The authors wish to express profound gratitude to Professor Hugo Devlieger and the neonatal nursing staff. This study is part of the Developmental Neurology Research Project, KU Leuven, Belgium. At present this research project is mainly supported by a grant from the Medical Research Council, Belgium (FGWO) and by a grant of `Kind en Gezin' (Flemish Child Health Organization), Belgium.

References (20)

There are more references available in the full text version of this article.

Cited by (40)

  • Specialized Neurological Studies

    2018, Volpe's Neurology of the Newborn
  • Flash visual evoked potentials in preterm infants

    2013, Ophthalmology
    Citation Excerpt :

    Brody et al24 and Kinney et al25 demonstrated in their detailed autopsy studies that the visual pathway has a briefer epoch of myelination than any other region in the developing human brain. These observations support the hypothesis that the progress in myelination in the human visual pathways can be detected by the study of the VEP peak latencies and that the preterm infants had an accelerated period in the visual system in early life.19 These observations may suggest that the outcome will be more effective and efficient if the visual interventions in preterm infants are made at a critical phase of development.

  • Orientation-reversal VEP: Comparison of phase and peak latencies in adults and infants

    2012, Vision Research
    Citation Excerpt :

    Although Fig. 3B seems to indicate that the infants’ P1 latency reached adult value as early as 30 weeks, infants’ latency remained statistically different from the adults’ for all age groups under 50 weeks. Similar to PR (Lee et al., 2012), the P1 latency decrease could be because of the progression of myelination with age (Dubois et al., 2008; Kos-Pietro et al., 1997; Tsuneishi & Casaer, 1997). However the individual variance among OR latencies is much higher than that for PR (Fig. 6A).

  • Visual Evoked Potentials in Infants and Children

    2012, Aminoff's Electrodiagnosis in Clinical Neurology
  • Neuromagnetic biomarkers of visuocortical development in healthy children

    2010, Clinical Neurophysiology
    Citation Excerpt :

    However, to our knowledge, the maturational changes of these components in children aged 6–17 years old have not been well investigated with MEG. Since visual evoked responses correlate to myelination and synaptic transmission (Scherg and Picton, 1991; Tsuneishi and Casaer, 1997), it is more than likely that VEFs change with age. However, due to the development of the brain, the size of the child’s head varies with age.

View all citing articles on Scopus
1

S. Tsuneishi is a clinical research fellow supported by a scholarship from an exchange program between the Flemish community of Belgium and Japan, and by the University of Leuven. Present address: Department of Pediatrics, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650, Japan. Fax: +81 78 3716239.

View full text