What is neonatal EEG?

Updated: Oct 03, 2019
  • Author: Rosalia C Silvestri-Hobson, MD; Chief Editor: Selim R Benbadis, MD  more...
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Neonatal electroencephalography (EEG) in infants has become valuable as a serial, noninvasive screening tool for infants at high risk of perinatal injuries. The brain dynamics and connectivity in different states (awake or asleep) can be defined, and a whole range of acute or chronic cerebral disorders can be identified. Such information often reveals presymptomatic or subclinical conditions.

The EEG prognostic value at the time of continuous development is often greater than at a later stage. EEG testing can provide reassurance to the physician and parents at a time of potential catastrophic damage.

The continuous changes that occur during early brain development are often associated with striking changes in EEG patterns over short periods. This makes it difficult to interpret EEG results, which can discourage the use of EEG testing.

Given the close relationships between certain morphological aspects of the developing brain and EEG results, gestational age can be reliably estimated (to ±1 wk) by EEG criteria. In fact, CNS development of the immature brain proceeds at about the same rate during fetal development as in the postnatal environment.

The physiological substrate for these early EEG patterns is unknown, but is probably derived from cortical generators that are strongly influenced by subcortical (primarily thalamic) afferent input. Rapid maturation of these structures (and not the corpus callosum) is most likely responsible for the interhemispheric synchrony that occurs close to full-term gestational age; in particular, rapid dendritic spine development and synaptogenesis are typical of the last month of fetal development. The complex development of cerebral sulci during this same period is probably responsible for the neonatal EEG results showing complex, more definitive patterns at term. At this age, easily recognizable and organized activity patterns appear. These continue with little change during the first month of life and are strictly characteristic of neonatal EEG.

There are several technical considerations when recording from a small (neonate) scalp. High skin resistance impedes low-resistance scalp-to-electrode contact. The state of activity (awake or quiet vs active sleep) can be selectively bound to certain aspects of pathology. It is important to annotate the tracing with particular attention to the presence and type of eye movements, facial movements, respiration (regular or irregular), sucking, crying, grimacing, and so on. Extracerebral monitors are needed in routine recordings, including at least electrooculogram (EOG), respiration rate measurement, and electrocardiogram (ECG). Only a reduced number of scalp electrodes, generally never more than the set in a 16-channel recording, are applicable. A low time constant (0.25–0.60 s) is preferable to record the low-frequency background activity. Slow paper speed maximizes the slow background and the degree of interhemispheric synchrony.

Recent technologic advances have promoted the use of amplitude integrated EEG (aEEG) to offer an accessible tool for bedside continuous cerebral monitoring. [1] However, this easy-to-use device requires nonetheless careful management and a vigilant well-trained staff. It also needs to complement standard conventional electroencephalography to be interpreted by experienced readers to avoid inappropriate conclusions and false positives, especially in the domain of neonatal seizures. As for amplitude measurements, 2-channel aEEG appears considerably more sensitive in detecting cerebral injury in the term encephalopathic infant, in comparison with a single-channel aEEG, especially in the setting of unilateral injury. [2]

For related information, see EEG Seizure Monitoring and Visual Analysis of Neonatal EEG.

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