High-frequency oscillations in neonatal EEG and their association with epilepsy

We assessed high-frequency oscillations (HFOs) in neonatal EEG hypothesizing that HFOs would be prevalent in neonates with prevailing or forthcoming severe epilepsy, fewer in those with benign epilepsy or acute provoked seizures, and absent in healthy neonates.

From a population-derived EEG database, we identified neonates with neonatal-onset epilepsy, chronic brain disease, acute stroke, perinatal hypoxic ischemic encephalopathy, acute brain infection, or no neurological diagnoses. We marked sleep stages, seizures, and HFOs manually, and evaluated outcome from medical records.

HFOs were detected in 29/98 (30 %) neonates, of whom 10 had ictal (median rate 0.53/min, range 0.07-6.41/min) and 24 had nonictal HFOs (median rate 0.20/min, range 0.01-20.99/min). Nonictal HFO occurrence and rate were significantly i) higher in neonates with neonatal-onset developmental and epileptic encephalopathy (DEE) than most other diagnostic groups, and ii) higher in neonates that later developed infantile-onset DEE (p < 0.05) than those surviving without DEE. Ictal HFOs were common during acute provoked seizures and were not linked with epilepsy.

Neonatal nonictal HFOs were associated with prevailing or forthcoming early-onset DEE.

Our data support the hypotheses that neonatal scalp HFOs are i) pathological, ii) associated with epilepsy severity, and iii) a marker of epileptogenesis.