Epileptic encephalopathies in early infancy.

Of the epileptic syndromes beginning in early infancy, we described the clinical and electrical characteristics of early myoclonic encephalopathy (EME) and Ohtahara syndrome (OS), and the differential diagnosis between the two syndromes, reviewing previous articles and our own study of 6 cases with EME and 15 cases with OS. With regard to the clinical seizure types, the main seizure type was tonic spasms in OS while myoclonias, especially erratic myoclonias, and frequent partial seizures were predominant in EME. The suppression-burst (S-B) pattern was a common feature of both syndromes, although their form, time of appearance, and duration of appearance differed considerably. The S-B pattern in OS was characterized by periodic and consistent appearances during both waking and sleeping states, whereas in EME, the S-B pattern was enhanced by sleep and often not manifested in the awake states. OS showed a specific pattern of evolution as age-dependent epileptic encephalopathy with concomitant EEG change while EME had no specific evolution with age. In OS, obvious brain lesions such as brain malformations were often seen. In contrast, frequent occurrence of familial cases suggested some kind of congenital metabolic disorder as the etiological factor in EME.