Definition:

Ring chromosome 20 syndrome is a chromosomal disorder that is characterized by mild to moderate intellectual disability and epilepsy, in the absence of significant diagnostic dysmorphic features. In most patients, seizures are drug resistant and characterized by prolonged nonconvulsive status epilepticus (NCSE). Psychomotor development may be normal or mildly delayed until epilepsy onset. The distinctive electroencephalograms (EEG) have been described in the syndrome. They suggest the involvement of the frontal lobes networks in the generation of ictal and interictal activities.