The intrauterine onset of convulsive syndromes has been documented only rarely, and previous reports have lacked detailed neuropathologic description. This report details a case of severe, intractable myoclonic encephalopathy, which, on the basis of severely abnormal paroxysmal fetal movement patterns confirmed by antenatal ultrasound, appears to have been of antenatal onset. The infant suffered an early demise and at autopsy showed features of a severe brain dysgenesis with polymicrogyria and superadded encephaloclastic features. Despite an extensive evaluation, the etiology of this condition remains elusive in our case. This case demonstrates that closer analysis of the qualitative features of fetal movements by, for instance, real-time ultrasound could aid in the antenatal diagnosis of neurologic, particularly convulsive, syndromes.