Abstract
Epileptic negative myoclonus (ENM) is a recently defined epileptic seizure type seen
in various epileptic syndromes. Although the long-term prognosis appears to be favorable,
the treatment of localization-related epilepsy (LRE) with ENM in childhood is sometimes
difficult due to the apparently pharmaco-resistant nature of ENM. We evaluated the
effects of antiepileptic drugs (AEDs) in 10 patients with ENM. Carbamazepine was administered
to eight patients, none of whom improved. Responses to clonazepam and valproic acid
were unpredictable, whereas ethosuximide (ESM) achieved complete control of ENM in
all six cases treated with this drug as adjunctive therapy. The pharmacological responses
of ENM to CBZ and ESM were quite similar to those of absence seizures. According to
the SPECT and ictal EEG findings in addition to the pharmacological responses from
this study, we favor to postulate that ENM is produced by a direct inhibitory action
on the motor cortex resulting in the interruption of voluntary muscle contraction
as generated by sharp-slow wave complexes, compatible with the mechanism considered
to underlie absence seizures. ENM are refractory to treatment and persisting if the
wrong AEDs, such as PHT or CBZ, are selected at the diagnosis of LRE. We recommended
a trial of ESM when ENM develops during the clinical course of LRE regardless of etiology.
Key words
Epileptic negative myoclonus - Idiopathic localization-related epilepsy - Ethosuximide
therapy -Absence seizure
