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EEG
EEG definitions vary, but paroxysms are considered to be seizures if they last more than 10
seconds. Neonatal electrographic seizures are often not sustained. The typical duration of the
electrographic neonatal seizure is 23 minutes15, but many seizures will be shorter, particularly
in preterm infants16. In spite of this, the total seizure burden can be very significant. Neonatal
seizures have a focal onset, whereas a generalised onset spike and wave seizure discharge is
extremely rare. Neonates can display simultaneous independent focal electrographic seizures
(Figure 1). Neonatal status is currently defined as a total seizure time occupying 50% of a
recording. Abnormal background activity is associated with an increased risk of seizures17,56
and poor neurodevelopmental outcome.
Discharges of less than 10 seconds’ duration have been termed BIRDs (brief inter-ictal
rhythmic discharges or brief ictal rhythmic discharges) and are of uncertain significance.
However, BIRDs have been associated with seizures in the same or subsequent EEG and with
poor neurodevelopmental outcome18.
EEG can provide confirmation that any suspicious phenomena are seizures. However, not all
clinically observed seizures are detected by EEG and many neonatal seizures are subclinical
(electro-cortical disassociation). Two explanations have been proposed: (1) some seizures may
originate at a subcortical level and are not propagated to surface electrodes because of the
immature synaptogenesis and cortical projections19 and (2) some subtle and tonic seizures
might not be epileptic but are primitive brain stem and spinal motor phenomena10.
Cerebral function monitoring
The cerebral function monitor (CFM) has the advantage that it is widely available, and
interpretation using pattern recognition can easily be learned. However, short seizures (<30
seconds) cannot be detected, low amplitude or focal seizures are easily missed and movement
artefacts are difficult to exclude and may look like seizures20. Thus, in neonates CFM is prone
to false-negative and false-positive errors. In particular, non-experts are prone to false negative
errors and the inter-observer agreement is low21,22,57.

Figure 1. Characteristic features of neonatal seizures: two simultaneous, but quite different
seizure pattern discharges over right and left hemispheres. There were no obvious clinical
manifestations (an example of electro-clinical dissociation).