How are paroxysmal patterns identified in the visual analysis of neonatal electroencephalogram (EEG)?

Updated: Aug 20, 2019
  • Author: Samuel Koszer, MD; Chief Editor: Selim R Benbadis, MD  more...
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Paroxysmal patterns: These include interictal discharges (positive rolandic sharp waves, frontal and temporal sharp transients), ictal discharges (focal spikes and sharp waves, pseudo delta, theta, alpha, and beta), and low-frequency discharge patterns.

  • Interictal patterns

    • While spikes or sharp waves are defined the same way in neonates, older children, and adults, their significance may be different. In many cases, spikes and sharp waves are normal features, especially in PT infants. Spikes and sharp waves are common during the bursting phase of TD or TA and may be observed over the temporal region during the inactive phase.

    • In healthy FT neonates, sporadic spikes predominate over frontal areas (usually synchronously) and are incorporated within the bursts of TA. They often coexist with rhythmic slow waves, misnamed "anterior slow dysrhythmia." These transients may shift between hemispheres; they begin to appear clearly at approximately 34-35 weeks' postconceptional age, persisting with diminished frequency into the beginning of the early infancy period. Because these spikes and sharp waves can be ontogenetically normal in spite of their epileptiform morphology, they have been labeled frontal sharp transients to defuse implications of an epileptiform signature.

    • Positive rolandic sharp waves are surface-positive, broad-based, sharp transients with duration up to 500 ms, localized over the rolandic areas (C3-C4). In spite of their paroxysmal features that might suggest an epileptiform signature, positive rolandic spikes do not correlate with ictal phenomena. Although these waves can be observed in the context of intracerebral hemorrhages, the present consensus is that they are associated more directly with pathologies that induce deep white matter lesions. Their underlying generator remains obscure, especially since explaining them simply based on white matter necrosis is difficult.

    • Positive temporal sharp waves are EEG transients with morphology and polarity similar to those of positive rolandic sharp waves; however, they occur over the midtemporal areas. They occur in neonates with intracranial hemorrhages or a history of perinatal asphyxia. See the image below.

      Positive temporal sharps. An infant of 41 weeks' p Positive temporal sharps. An infant of 41 weeks' postconceptional age with a fever (temperature, 102°F) and 3 episodes of right arm and leg jerking with eye deviation that last 5-10 seconds each. Left positive temporal sharps are seen in the 4th and 5th seconds at T3 and independently at T4 during the 8th second.
    • A clear differentiation between normality and abnormality for spikes and sharp waves may be difficult because the boundaries still are not distinct and are a matter of controversy. Spikes and sharp waves that occur over frontal, rolandic, and temporal areas are abnormal if they are excessively frequent for the postconceptional age, appear in short runs, are consistently unilateral, occur frequently during the attenuated phase of TA, or persist during the more continuous patterns of REM sleep or wakefulness. See the image below.

      Excessive sharp transients. An infant of 36 weeks' Excessive sharp transients. An infant of 36 weeks' postconceptional age with hypoxic ischemic encephalopathy and seizures on days 2 and 3 of life. Sharp transients are seen in the 1st and 3rd seconds at T4.
    • The significance of excessive numbers of spikes and sharp waves is not clear. While excessive numbers of spikes and sharp waves are more common in neonates with seizures than in neonates without them, the correlation is tenuous. Many neonates with electroencephalographic and/or behavioral seizures may have few interictal spikes or sharp waves. Conversely, the presence of excessive spikes or sharp waves can be seen in neonates without a history of seizures.

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