Ethosuximide completely suppressed epileptic negative myoclonus in childhood localization-related epilepsy

Abstract

We report two cases of localization-related epilepsy manifesting frequent brief atonia. The patients were assumed to have epileptic negative myoclonus (ENM), and were successfully treated with ethosuximide (ESM). Both exhibited hemi-orofacial twitches during sleep, and interictal electroencephalography (EEG) showed paroxysms over the contralateral posterior-temporal and centroparietal regions. Incessant atonia appeared at nine and 10 years of age accompanied by motor paresis. Ictal EEG showed irregular high-voltage spike-waves predominantly over bilateral centroparietal regions. Carbamazepine and zonisamide were ineffective in controlling, or even aggravated ENM. The addition of ESM resulted in immediate and complete disappearance of ENM and partial motor seizures along with an improvement of motor paresis. The first case was assumed to have idiopathic etiology because of normal development before the onset of epilepsy, while the second case was considered to have cryptogenic etiology based on a pre-existing intellectual disability. Hence, we recommend that ESM should be considered for the treatment of ENM that develops during the course of localization-related epilepsy, regardless of the etiology. However, further studies are still needed to evaluate the effects of ESM in the treatment of ENM.