Extrauterine life duration and ontogenic EEG parameters in preterm newborns with and without major ultrasound brain lesions

doi:10.1016/j.clinph.2005.08.020

Clinical Neurophysiology

Volume 116, Issue 12, December 2005, Pages 2796-2809

https://doi.org/10.1016/j.clinph.2005.08.020 Get rights and content

Abstract

Objective

To determine whether extrauterine life duration is associated with different ontogenic electroencephalographic (EEG) patterns in premature infants compared with neonates born at later gestational ages (GAs).

Methods

We included 97 preterm infants of 24–36 weeks GA. We performed neurosonography and EEG recordings at week 1 and 2 of postnatal life, then every two weeks until term conceptional age (CA). We analyzed background EEG and sleep states and compared them at matched CA.

Results

In the group of infants without major ultrasound lesion (MUL), those <29 weeks GA showed increased sawtooth at 32–36 weeks CA and delta brushes from 34 to 40 weeks CA compared to infants ≥29 weeks GA. Infants with MUL compared to those without MUL showed significantly longer interburst intervals, shorter minimum burst duration at 2 and 4 weeks postnatal life, and higher incidence of sawtooth and delta brushes from 34 weeks CA to term. In addition, those of <29 weeks GA had higher rates of indeterminate sleep until 32 weeks CA. The type of MUL most frequently associated with dysmature EEG patterns was persistent ventricular dilatation.

Conclusions

Premature infants without MUL showed prolonged dysmature EEG patterns as from early CAs (≥29 weeks). This finding was more evident in those with MUL.

Significance

Extrauterine EEG development in prematures may differ from that of babies born at a later GA.

Introduction

Electroencephalographic (EEG) recordings may be used to estimate conceptional age (CA) of neonates with less margin of error than any other method (Scher et al., 1994a, 1995). However, certain nonage-related factors may modify ontogenic EEG patterns. Intrauterine stress, e.g. a fetus with retarded growth, may give rise to accelerated cerebral maturation (Amiel-Tison and Pettigrew, 1991). Other premature infants may show delayed maturational EEG patterns. In some premature infants, such as those with respiratory disease, the delay may be transient and without prognostic implications, (Holmes et al., 1979); in others the delay may be persistent and associated with poor outcome (Hahn and Tharp, 1990). Maturational EEG patterns may be significantly altered by encephalopathy in premature infants, and if this EEG alteration is observed at more advanced CA, it may have prognostic implications (Biagioni et al., 1994. Tharp et al., 1981).

Premature infants, at term CA and without serious observable disease during hospitalization, have presented significant differences in EEG patterns and in sleep states compared with full-term infants (Scher et al., 1996, 2003). However, there is no information about different maturational EEG patterns (including the developing sleep states) in very premature newborns with or without manifest CNS pathology at early matched CAs. If we can demonstrate exactly when these differences manifest and how long they persist, we could interpret EEG tracings more accurately in the postnatal life of preterm infants.

We studied a large group of preterm newborns, with and without major ultrasound brain lesions (MULs), using repeated polysomnographic recordings from birth to 40–42 weeks CA in order to: (1) to determine whether increased extrauterine life duration is associated with more dysmature ontogenic EEG patterns (including developmental sleep states); (2) compare several EEG patterns and their corresponding sleep states in infants with and without MUL at different matched CAs; (3) follow those with MUL to determine the duration of significant abnormalities of background EEG and sleep states; and (4) attempt to elucidate whether certain specific ultrasound findings are associated with persistent EEG abnormal maturational patterns.

Section snippets

Patients

We studied 97 preterm infants with a gestational age (GA) ranging from less than 27 to 36 weeks, hospitalized in our neonatal unit between 1993 and 1998. Parental consent was obtained after explanation of the methods and aim of the study. Relevant clinical characteristics are shown in Table 1. Infants who died before 42 weeks CA or who had chromosomal abnormalities and/or multiple congenital malformations were excluded from this study. Gestational age was calculated from the date of the

Background EEG activity

The results (mean and standard deviation) obtained from newborns with and without MUL of different GAs and at matched CAs are shown in Table 2, Table 3.

Discussion

In this study we performed a series of EEG recordings in newborns of different GAs until they reached term CA. Our objective was to test whether the more premature infants presented observable differences in background EEG and sleep patterns compared with those born at more advanced GAs at matched CAs, including term CA.

Our study was based on the results obtained in two groups of premature infants: one with major ultrasound lesions and the other without. To facilitate understanding, we have

Acknowledgements

The authors wish to thank Michael Lee McLean for help in writing this version of the manuscript.

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Extrauterine life duration and ontogenic EEG parameters in preterm newborns with and without major ultrasound brain lesions

Abstract

Objective

Methods

Results

Conclusions

Significance

Introduction

Section snippets

Patients

Background EEG activity

Discussion

Acknowledgements

Brain Dev

Electroencephalogr Clin Neurophysiol

Clin Neurophysiol

Clin Neurophysiol

Electroencephalogr Clin Neurophysiol

Electroencephalogr Clin Neurophysiol

Electroencephalogr Clin Neurophysiol

Neurophysiol Clin

Pediatr Neurol

Electroencephalogr Clin Neurophysiol

Pediatr Neurol

Clin Neurophysiol

Clin Neurophysiol

Electroencephalogr Clin Neurophysiol

Brain Dev

Brain Dev