BURST SUPPRESSION AND IMPAIRMENT OF NEOCORTICAL ONTOGENY - ELECTROCLINICAL AND NEUROPATHOLOGIC FINDINGS IN 2 INFANTS WITH EARLY MYOCLONIC ENCEPHALOPATHY

We report the electroclinical and neuropathologic correlations in 2 ch ildren aged 2.5 months affected by early myoclonic encephalopathy char acterized by epileptic seizures, erratic myoclonus, and an EEG pattern of burst suppression. Despite different etiologies, the neuropatholog ic findings showed similar abnormalities in both cases, with no substa ntial impairment of the myelination processes. Islands of matrix tissu e scattered in the periventricular region and neurons aligned marginal ly in the bulbar olives were detected. The presence of numerous large spiny neurons dispersed in the white matter along the axons of the cor tical gyri was the most striking finding. These neurons have been inte rpreted as abnormally persisting interstitial cells in 2.5-month-old c hildren. These early generated neurons, normally present during neocor tical histogenesis, are programmed to die near the end of gestation or soon after birth. The interstitial cells are regarded as a waiting co mpartment of afferent fibers during cortical development. Their persis tence in our patients represents an anatomic condition for cortical di sconnection providing a pathophysiologic basis to burst-suppression ph enomena.