Ring chromosome 20 syndrome: Electroclinical description of six patients and review of the literature

BackgroundRing chromosome 20 syndrome is a rare chromosomal disorder.MethodsIn six patients, we focused on the presenting epileptic phenotype, the behavioral and mental problems and the relationship between the ratio of mosaicism and the age at onset of the epilepsy.ResultsAll patients presented with pharmacoresistant frontal lobe complex partial seizures. The earliest onset of epilepsy was seen in patients without mosaicism. There were three patients out of six with behavioral disturbances before the onset of seizures. All patients had mild to moderate cognitive impairment. Electroencephalogram recordings showed rhythmic theta waves with frontal predominance and non-convulsive status epilepticus (NCSE).ConclusionsThe ring chromosome 20 syndrome is characterized by childhood-onset refractory epilepsy continuing throughout adult life, mental disability, and behavioral disturbances which can originate before seizure onset. Ictal EEG reveals a unique pattern. Our findings indicate a possible link between the percentage of affected cells and the age of epilepsy onset.

► This paper shows the clinical variability of the R20 syndrome.
► Behavioural and cognitive problems can be present before the epilepsy-onset.
► Patients with R20 have refractory epilepsy and are mentally retarted at adult age.
► There is a relationship between epilepsy onset and the percentage R20 cells.