Original articlesElectroencephalography in neonatal seizures: Comparison of a reduced and a full 10/20 montage
Introduction
Electroencephalography (EEG) is an important clinical tool in the identification of neonatal seizures, estimation of central nervous system maturity, and assessment of prognosis in neonatal encephalopathy [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. Accurate diagnosis of neonatal seizures requires skilled clinical staff, and is greatly assisted by the use of EEG, and clinical assessment alone is an insensitive method of quantifying neonatal seizures [14], [15]. In newborns treated with antiepileptic medications for seizures, electroclinical dissociation may occur, with continuing electrographic seizures without clinical manifestation [16], [17]. Continuous EEG monitoring of such infants may therefore be important not only for diagnosis, but also for assessment of the efficacy of intervention [8], [17]. Guidelines published by the American Electroencephalography Society (now the American Clinical Neurophysiology Society) recommend either a full (16 electrodes) montage, or a reduced (9 electrodes) montage, with four additional channels devoted to polygraphic variables (respiration, eye movement, electrocardiogram, electromyography) [18]. The potential advantages of using a reduced montage in these ill infants include: shorter electrode application time reducing the risk of heat loss, decreased handling of vulnerable infants, and increased scalp space for performance of cranial ultrasound and/or intravenous access. However, while it is known that extremely reduced (4 electrodes) montages may fail to identify topographically restricted seizures [19], comparison of a reduced (9 electrodes) montage with a full montage has not been reported. With the advent of digital technology, it has become possible to “remontage” previously recorded EEGs for such a comparison.
In this study, the sensitivity, specificity, and predictive value of a reduced montage (RM, 9 electrodes) for the detection of electrographic seizures and for assessment of background abnormalities are defined, in comparison to a full 10/20 electrode montage (FM, 19 electrodes).
Section snippets
Material
One hundred fifty-one neonatal EEG records, obtained between March 1999 and October 2001, were retrospectively obtained from the master database in the Bio-logic System of the Clinical Neurophysiology Laboratory, Children’s Hospital, Boston. The EEGs had been recorded using a full 10/20 electrode array with additional polygraphic channels. For the purpose of blinded analysis, each EEG file was given a study code number and patient names were deleted from the records before analysis.
EEG montages
A digital
Subject data
A total of 151 EEG recordings were obtained from 139 infants, between 29 and 48 weeks conceptional age. Ages at recording were as follows: ≪30 weeks: 2; 30 to 33 weeks: 3; 34 to 37 weeks: 14; 38 to 40 weeks: 51; 41 to 44 weeks: 72; and 45 to 48 weeks: 9. Among the 151 EEG records, 126 were routine neonatal EEG recordings, 35 were prolonged bedside EEG recordings. Seventy-two EEG files included a video-EEG recording.
Electrographic seizures
Using the FM, a total of 187 seizures were identified in 31 EEGs obtained from
Discussion
Neonatal electrographic seizures are typically focal in nature and topographically restricted [22], [28], [29], [30]. Seizures may be missed when using a limited number of electrodes. Some laboratories use full 10/20 electrode montages (FM) to detect neonatal electrographic seizures more reliably. Handling time and head mobilization maneuvers of babies increase in proportion to the number of electrodes applied. For these reasons, double-distance electrode placement is used in some laboratories.
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