Combination of infantile spasms, non-epileptic seizures and complex movement disorder: a new case of ARX-related epilepsy.

Mutations in the ARX gene are responsible for a wide variety of mental retardation conditions including X-linked infantile spasms (ISSX) and generalized dystonia. However, electroclinical descriptions in patients with ISSX carrying ARX mutations are scarce. Here, we report on the electroclinical features of a 4-year-old boy with an expansion of the trinucleotide repeat in the ARX gene. Epilepsy started at 2 months of age with subclinical spasms that consisted of episodes of eye rolling combined with atypical hypsarrhythmia. Later, the condition evolved into severe mental retardation with polymorphic ictal episodes that consisted of nocturnal brief axial contractions followed by dyskinetic movement of all four limbs and diurnal clusters of chaotic movements combined with myoclonic jerks. EEG recording of these episodes lead to the diagnosis of non-ictal dyskinetic movements. This combination of early infantile spasms followed by a complex movement disorder contributes further to extent the pleiotropy of the ARX-linked "interneuronopathy" and should lead the clinician to ARX mutation screening.