Repetitive EEG recordings are necessary for the diagnosis of early myoclonic encephalopathy

Early myoclonic encephalopathy (EME) is a rare malignant epileptic syndrome. The erratic myoclonus with or without focal motor seizures, time of onset before 3 months of age, and suppression-burst (SB) pattern in EEG are accepted as the diagnostic criteria for EME. We report a 40-day-old infant with the diagnosis of non-ketotic hyperglycinemia (NKHG). The infant developed myoclonic and focal tonic seizures on the first day of life. His first sleep EEG recorded after onset of seizure was normal. Because of the diagnosis of NKHG and early developed myoclonic seizure, we thought the infant might be EME, and repeated sleep EEG on admission in which asymmetrical SB pattern was seen. We concluded that the absence of SB pattern in the first EEG recording does not exclude the diagnosis of EME, but repetition of EEG is necessary to demonstrate the presence of SB pattern to meet the diagnostic criteria for EME.