High-Frequency Oscillations in Surface EEG Recorded from Neonates with Perinatally Acquired Hypoxic Ischemic Encephalopathy: A Retrospective Study

Background/Purpose: High-frequency Oscillations (HFO) are relatively new biomarkers in intracranial EEG that can help to specifically delineate brain regions that generate epileptic seizures. Recent studies revealed that HFO can be detected in childhood surface EEG and that their frequency correlates to disease activity. The neonatal brain is susceptible to hypoxic damage and tends to generate epileptic seizures due to immaturity. 40 to 60% of children with hypoxic brain damage develop seizures; 10 to 20% of them develop chronic epilepsy. Aim of this study was to assess if the immature neuronal networks of newborns generate HFO as evidence of epileptogenicity.

Methods: Long-term EEG recordings of 42 neonates who were treated in a neonatal intensive care unit in the University Children´s Hospital Freiburg or Lucile Packard Children's Hospital Stanford (USA) because of hypoxic brain damage were analyzed.

Results: Of 42 long-term EEG recordings that were analyzed, 22 showed moderately or severely reduced EEG background activity. While only nine of the EEG recordings had sufficient data quality that allowed for visual HFO-detection, HFO could be detected in eight of these. HFO were detected with a mean rate of 0.22 ± 0.19 events per minute.

Conclusion: HFO can be detected in surface EEG of neonates with perinatally acquired hypoxic brain damage. However, the data quality needed for visual HFO detection is hard to obtain in the environment of intensive care. A clinical follow-up is needed to correlate HFO detected during the acute illness to the development of chronic epilepsy.