What are the EEG changes characteristic of neonatal seizures?

Updated: Oct 01, 2020
  • Author: Raj D Sheth, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

Generalized seizures are rare in neonates. Many of the so-called subtle, generalized tonic, and multifocal myoclonic seizures do not have an electroencephalographic (EEG) correlate. These movements in the severely affected infant may represent brain stem release phenomena. Focal seizures, particularly clonic seizures, are highly associated with EEG changes. Thus, EEG plays a crucial role in the evaluation of neonatal seizures. The EEG changes significantly with gestational age; therefore, calculation of gestational age and familiarity with age-specific norms is crucial in interpretation of the EEG in infants.

Two well-defined EEG seizure patterns are seen in neonates, as follows:

  • Seizures with focal low-frequency electrographic correlates: These patterns may occur at 1-1.5 Hz frequency and are generally seen in severe cerebral insults, such as severe hypoxic-ischemic encephalopathy.

  • Seizures with focal high-frequency electrographic correlates: These patterns typically evolve over 10-20 seconds and are usually seen with focal cerebral insults, such as strokes. Strokes in the neonate, unlike in the older individual, are typically associated with porencephalic cysts. Porencephalic cysts result from strokes that involve large portions of the cerebral parenchyma (ie, loss of both gray and white matter leading to a communication between the subarachnoid space and the cerebral ventricles).

For more information, see Benign Neonatal Convulsions.


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