Age-dependent epileptic encephalopathy: a longitudinal study.

A longitudinal clinico-electroencephalographic study was conducted on 484 cases of age-dependent epileptic encephalopathy; early-infantile epileptic encephalopathy with suppression-burst (Ohtahara) (EIEE), the West and Lennox syndromes. 1) The three types had the same kind of etiologic heterogeneity. 2) An evolutional change with age was noted from EIEE to the West and from the West to the Lennox syndromes, with the change from suppression-burst to hypsarhythmia, and from hypsarhythmia to the diffuse slow spike-waves. 3) The core ictal EEG pattern of tonic spasms was the desynchronization in EIEE and the West syndrome, with the rapid synchronization and recruiting rhythm in the Lennox syndrome. In the same cases, the changes from desynchronization to hypersynchronization were observed with age. These facts suggest that the three syndromes are based on the same pathophysiology, strongly related to the subcortical mechanism, and that their clinico-electrical manifestations are modified by the degree of brain maturation.