The authors report the clinical features, electroencephalography (EEG), neuroimaging (brain magnetic resonance image-MRI), and cytogenetic findings of a young female patient with rare cytogenetic anomalies characterized by de novo 46, XX, r (20)(p13q13.3). The patient had a history of mild mental retardation, emotional liability and intractable epilepsy with non-convulsive status epilepticus. The MRI brain showed focal cerebral dysplasia over the left temporal region. The multiple
seizures were refractory to antiepileptic medications and prolonged, confused state with or without a motor component. The continuous video-EEG monitor showed epileptiform discharges over bilateral frontal regions with frontal origin. The symptoms were relieved after midazolam infusion. A patient who was present with intractable epilepsy with continuous frontal epileptiform discharges, mental retardation, abnormal behavior, without dysmorphic features should be suspected of chromosomal abnormalities especially ring chromosome 20.

Keywords: Ring chromosome 20, Epileptic encephalopathy, Non-convulsive status epilepticus