The Controversy Regaring Criteria for Early Myoclonic Encephalopathy

Abstract

To re-evaluate the diagnostic criteria for early myoclonic encephalopathy (EME), the following study was done. During the past 2 years, five patients with erratic, fragmentary myoclonus of neonatal onset, in association with other types of seizures, were analyzed with regard to etiologies, electroclinical features and their evolution, using a series of examinations including electroencephalographies (EEGs) and metabolic investigations. Of these five patients, three were diagnosed to have non- ketotic hyperglycinemia (NKH); one was pyridoxine-dependent; the other was cryptogenic. Only two cases (one NKH and one cryptogenic) had initial typical suppression-burst (S-B) EEG pattern, which subsequently evolved into multiple paroxysmal abnormalities with random asynchronous attenuation (MP-AA) pattern. The other two cases with NKH had MP-AA EEG pattern throughout both awake and sleep recordings in two consecutive EEG studies. All three cases with NKH survived with increasing microcephaly, muscle tonicity; all developed infantile spasm with hypsarrhythmia on EEGs . The patient with pyridoxine- dependency had an initial MP-AA EEG pattern , which converted into S-B pattern after the first use of pyridoxine, eventually becoming normal after a supplement with the second-dose of pyridoxine. In conclusion, either S-B or NIP- AA pattern may reflect the severity of the underlying pathologies or the disease stages. These results suggest that, from both etiological and electroclinical viewpoints , EME may represent a broader spectrum than previously recognized. The still ongoing controversy regarding whether the S-B pattern should be recognized as the sore EEG criteria for the diagnosis of EME needs further experience to clarify. (C) 1998 Elsevier Science B.V. All rights reserved .