Interictal epileptogenic fast oscillations on neonatal and infantile EEGs in hemimegalencephaly

SummaryPurposeHemimegalencephaly is an epileptic encephalopathy which presents during the neonatal period. Our aims are to analyze interictal fast oscillations and EEG patterns in neonates and infants with hemimegalencephaly.MethodsWe collected scalp EEGs and applied multiple band frequency analysis (MBFA) to analyze frequency and power of interictal fast oscillations (FOs).ResultsWe studied 18 scalp EEGs in 7 patients with catastrophic epilepsy secondary to hemimegalencephaly, between 3 days and 24 months of age. Maximum frequency of FOs (22–57 Hz; mean, 42 Hz) on the hemimegalencephalic side was significantly higher than those (8–27 Hz; mean, 18 Hz) in the unaffected side (p < 0.05). Differences in maximum FOs remained within 1–8 Hz (mean, 3 Hz) across consecutive EEGs. We found four EEG patterns: (1) suppression burst pattern (7 EEGs, 6 patients), (2) continuous triphasic complex pattern (5 EEGs, 3 patients), (3) continuous high amplitude slow waves with spikes (3 EEGs, 2 patients) and (4) frequent spike and slow waves (3 EEGs, 2 patients). Five patients with multiple EEG recordings showed changing EEG patterns.ConclusionWe confirmed the interictal epileptogenic FOs in neonatal EEGs of patients with hemimegalencephaly. The frequency of epileptogenic FOs remains stable from the neonates through increasing age while the patterns of EEG changed during brain maturation.