Frontal motor seizure following non-convulsive status epilepticus in ring chromosome 20 syndrome.

The ring chromosome 20 syndrome is a rare syndrome characterized by intractable epilepsy with particular electro clinical features including episodes of prolonged confusional state and nocturnal frontal lobe seizures. We report a 17-year-old girl who had intractable epilepsy with frontal seizure and prolonged confusional state secondary to non-convulsive status epilepticus. The diagnosis of ring chromosome 20 was suspected and confirmed by karyotype. The cytogenetic study of CHRNA4 and KCNQ2 genes did not detect deletion in the ring chromosome 20. During video-EEG recording, this girl presented a non-convulsive status epilepticus that lasted more than 20 minutes followed by typical frontal lobe seizure. This association was not previously described, and was probably caused by chromosomal instability.