Electroclinical characterization and classification of symptomatic epilepsies with very early onset by multiple...

To characterize very early onset symptomatic epilepsies electroclinically, to identify meaningful factors to delineate epilepsy syndromes under this category, and to test validity of the current syndromic organization of these epilepsies by the International League Against Epilepsy (ILAE).

Subjects were 38 epileptic patients with seizure onset before 3 months of age. We investigated the age of seizure onset, seizure types, myoclonus, EEG features, neuroimaging studies, outcome of seizures and development. We performed multiple correspondence analysis (MCA) to reveal associations among these characteristics and to find important characteristics to divide this epilepsy group into subgroups.

Very early onset epilepsies were characterized by partial seizures and epileptic spasms, especially occurring in combination as a single ictal event (combined seizures), and poor outcome. Suppression-burst (SB), hypsarrhythmia, EEG asymmetry and structural brain abnormalities were common. MCA demonstrated that presence or absence of SB was the most meaningful factor to separate this group into subgroups. MCA on the subgroup with SB revealed a subset with early-onset spasms, partial seizures with single focus, no myoclonus, SB during wakefulness and sleep, no EEG asynchrony, hypsarrhythmia and combined seizures, and another subset with late-onset spasms, partial seizures with multiple foci, myoclonus, EEG asynchrony, no combined seizures, SB during sleep only, no EEG asymmetry, no structural abnormality and no hypsarrhythmia. These corresponded to Ohtahara syndrome and early myoclonic encephalopathy, respectively.

Very early onset symptomatic epilepsies have the electroclinical characteristics distinct from those with later onset. This study supported the current ILAE organization on this epilepsy group from statistic approach.