Abstract

Ring chromosome 20 syndrome is a rare disorder characterized by intractable epilepsy and cognitive dysfunction, in some associated cases by cognitive decline. In most cases, it is an underdiagnosed condition as chromosome analysis is not routinely performed in intractable epilepsy for the reason that the phenotype is usually normal. A case of a 15-year-old girl is reported. She had had frequent episodes of complex partial seizures with oral automatism, absences and occasional generalized seizures since the age of 7 years. Treatment with several classical and new antiepileptic drugs was ineffective.  Her cognitive functions deteriorated with time. Interictal EEG revealed bilateral slow spike-waves of 2.5–3 Hz with frontal predominance. Chromosome analysis revealed a karyotype of 46,XX r(20) in 48% of cells (mosaicism of the karyotype). The karyotype of her mother was normal: 46,XX. Valproate 1000 mg per day and lamotrigine 200 mg per day were prescribed and the frequency of epileptic fits diminished to 1–2 fits per week.

In conclusion, karyotype analysis should be performed in every patient with intractable epilepsy of unknown aetiology.