We report a patient with early infantile epileptic encephalopathy (EIEE) with suppression-burst (Ohtahara syndrome) associated with olivary-dentate dysplasia and agenesis of mamillary bodies is reported. Although those with Ohtahara syndrome are a heterogeneous group, virtually all reported cases are secondary to neuronal migrational disorders, sometimes only identified by detailed neuropathologic examination, as in this case report, which describes mamillary body agenesis as a not-yet-recognized anomaly associated with Ohtahara syndrome. All children with Ohtahara syndrome should have high-resolution magnetic resonance imaging (MRI) and detailed postmortem neuropathologic examinations.