THE CONTROVERSY REGARDING DIAGNOSTIC-CRITERIA FOR EARLY MYOCLONIC ENCEPHALOPATHY

To re-evaluate the diagnostic criteria for early myoclonic encephalopa thy (EME), the following study was done. During the past 2 years, five patients with erratic, fragmentary myoclonus of neonatal onset, in as sociation with other types of seizures, were analyzed with regard to e tiologies, electroclinical features and their evolution, using a serie s of examinations including electroencephalographies (EEGs) and metabo lic investigations. Of these five patients, three were diagnosed to ha ve non-ketotic hyperglycinemia (NKH); one was pyridoxine-dependent; th e other was cryptogenic. Only two cases (one NKH and one cryptogenic) had initial typical suppression-burst (S-B) EEG pattern, which subsequ ently evolved into multiple paroxysmal abnormalities with random async hronous attenuation (MP-AA) pattern. The other two cases with NKH had MP-AA EEG pattern throughout both awake and sleep recordings in two co nsecutive EEG studies. All three cases with NKH survived with increasi ng microcephaly, muscle tonicity; all developed infantile spasm with h ypsarrhythmia on EEGs. The patient with pyridoxine-dependency had an i nitial MP-AA EEG pattern, which converted into S-B pattern after the f irst use of pyridoxine, eventually becoming normal after a supplement with the second-dose of pyridoxine. In conclusion, either S-B or NIP-A A pattern may reflect the severity of the underlying pathologies or th e disease stages. These results suggest that, from both etiological an d electroclinical viewpoints, EME may represent a broader spectrum tha n previously recognized. The still ongoing controversy regarding wheth er the S-B pattern should be recognized as the sore EEG criteria for t he diagnosis of EME needs further experience to clarify. (C) 1998 Else vier Science B.V. All rights reserved.