A standardised assessment scheme for conventional EEG in preterm infants

Highlights

• A standardised scheme for preterm EEG assessment at different post-menstrual age is needed.

• We have developed a standard EEG assessment scheme for preterm infants.

• Good interobserver agreement is achieved using the present scheme.

Abstract

Objective

To develop a standardised scheme for assessing normal and abnormal electroencephalography (EEG) features of preterm infants. To assess the interobserver agreement of this assessment scheme.

Methods

We created a standardised EEG assessment scheme for 6 different post-menstrual age (PMA) groups using 4 EEG categories. Two experts, not involved in the development of the scheme, evaluated this on 24 infants <32 weeks gestational age (GA) using random 2 hour EEG epochs. Where disagreements were found, the features were checked and modified. Finally, the two experts independently evaluated 2 hour EEG epochs from an additional 12 infants <37 weeks GA. The percentage of agreement was calculated as the ratio of agreements to the sum of agreements plus disagreements.

Results

Good agreement in all patients and EEG feature category was obtained, with a median agreement between 80% and 100% over the 4 EEG assessment categories. No difference was found in agreement rates between the normal and abnormal features (p = 0.959).

Conclusions

We developed a standard EEG assessment scheme for preterm infants that shows good interobserver agreement.

Significance

This will provide information to Neonatal Intensive Care Unit (NICU) staff about brain activity and maturation. We hope this will prove useful for many centres seeking to use neuromonitoring during critical care for preterm infants.

Introduction

Conventional EEG is a reliable tool for the assessment of neonatal brain activity and has been extensively shown to correlate with outcome (Tharp et al., 1981, Watanabe et al., 1983, Clancy et al., 1984, Radvanyi-Bouvet et al., 1987, Biagioni et al., 1996, Marret et al., 1997, Watanabe et al., 1999, Biagioni et al., 2000, Maruyama et al., 2002, Le Bihannic et al., 2012, Lloyd et al., 2016).

Due to the increasing survival rates of very and extremely preterm infants, there is an urgent need to provide well-defined boundaries between normal and abnormal EEG features at different post-menstrual age (PMA) and to objectively evaluate brain activity and maturation.

Although the EEG characteristics of preterm and term infants are vastly different, the existing EEG assessment systems have been developed for mixed populations of both preterm and term infants (Watanabe et al., 1999, Holmes and Lombroso, 1993). These assessment schemes lack a more systematic approach of identifying specific features of the preterm EEG, which develop with PMA. This is evident in a recently developed system, named the ‘standardized computer-based organised reporting of EEG’ (SCORE), which provides a standard way of reporting EEG without attempting to grade the EEG (Beniczky et al., 2013, Beniczky et al., 2017). As this is a system targeting infants at all age groups, there are no specific EEG features defined for preterm infants at varying PMA. A specific EEG scoring system for very preterm infants was recently developed to predict neurodevelopmental outcome (Perivier at al., 2016). However, this score is inserted in a multimodal evaluation which includes EEG surveillance, clinical assessment at discharge and cerebral imaging for outcome assessment. This approach is similar to previous studies of preterm infants (Pisani et al., 2008, Pisani et al., 2016, Lloyd et al., 2016), in which EEG grading systems have been used together with other parameters to predict outcome (Holmes and Lombroso, 1993, Watanabe et al., 1999).

Therefore, the aim of our study was to develop a method, which was as objective as possible, to evaluate and analyse normal and abnormal EEG features in preterm infants, at different ages and to assess the interobserver agreement of this method when tested by two experts independently.