A case of atypical benign partial epilepsy with action myoclonus

We describe a boy, 3 years and 6 months old, who experienced a rolandic seizure accompanied by a cluster of atypical absence seizures, the EEGs for which corresponded to those of atypical benign partial epilepsy (ABPE). Of note, this patient suffered from developmental delay beginning in infancy and exhibited giant middle-latency somatosensory evoked potentials with action myoclonus. With the exceptions of ethosuximide, acetazolamide, and adrenocorticotropic hormone, which have been reported to be effective in ABPE, the atypical absence seizures were intractable despite extensive treatment with various anticonvulsants. The drugs that were effective led to a remarkable reduction in seizure frequency and EEG improvement, but the efficacy was temporary. The patient demonstrated moderate mental retardation without regression and could not walk with support or speak any meaningful words at the age of 3 years and 6 months. Based on thorough differential diagnosis, although further studies will be necessary, we propose that this boy may present a new phenotype of ABPE: ABPE with action myoclonus.