Ohtahara syndrome: With special reference to its developmental aspects for differentiating from early myoclonic encephalopathy

Ohtahara syndrome (OS) is well known as a peculiar early onset epileptic syndrome with serious prognosis. The outline of OS, mainly in relation to the evolution with age, and differentiation from related conditions, particularly early myoclonic encephalopathy (EME) were mentioned.Etiologically, structural brain lesions are most probable in OS, and non-structural/metabolic disorders in EME. Clinically, tonic spasms are the main seizures in OS, while myoclonia and frequent partial motor seizures in EME. Another difference is noted in EEG findings: suppression-bursts (SB) are consistently observed in both waking and sleeping states in OS, but suppression-bursts become more apparent in sleep in EME. The course observation clarifies differences between both syndromes; SBs evolve to hypsarrhythmia around 3-4 months of age, and sometimes further to diffuse slow spike-waves in OS. In contrast, in EME suppression-bursts may persist up to late childhood after a transient evolution to hypsarryhtmia in the middle to late infancy. Transition between syndromes is also specific; OS evolves to West syndrome, and further to Lennox-Gastaut syndrome with age, but EME persists long without such evolution excepting a transient phase of West syndrome.These clinicoelectrical characteristics and differential points strongly indicate the efficiency of the developmental study to delineate both syndromes.