Clinical and neurophysiology study of 17 children with epileptic negative myoclonus

Abstract

BACKGROUND: Epileptic negative myoclonus (ENM) is a clinically underrecognized seizure type, and systematic data on its clinical manifestations and optimal management strategies in pediatric populations remain scarce. This case series aimed to describe the clinical manifestations, neurophysiological patterns, and therapeutic outcomes in pediatric ENM. METHODS: A retrospective descriptive analysis was conducted on 17 ENM patients diagnosed at Wuxi Children's Hospital between October 2017 and June 2024. Clinical data, electroencephalogram (EEG) findings, and treatment responses were systematically evaluated. RESULTS: The cohort showed a marked female predominance (female-to-male ratio of 12:5). All cases exhibited upper-limb ENM, with contralateral central-parietal epileptiform discharges observed in ictal EEG. Two patients presented additional lower-limb ENM accompanied by midline discharges. Clinically, ENM manifested as the initial symptom in five cases (29.4%), including two with isolated ENM. Therapeutic outcomes varied: among four non-electrical status epilepticus during sleep (ESES) patients, antiseizure medications (ASMs) achieved symptom control, including one case of oxcarbazepine (OXC)-associated ENM that resolved after transition to valproate (VPA). Of 13 ESES-positive patients, three responded to ASMs alone, while nine received methylprednisolone pulse therapy (MPT), and one surgical candidate with focal cortical dysplasia (FCD) type IIa achieved post-resection remission. Among the nine children treated with MPT: four showed a good response; four relapsed upon steroid withdrawal; and one responded well to ketogenic diet (KD) therapy. CONCLUSIONS: ENM can manifest as the initial or sole epilepsy symptom in children. The marked female predominance in this cohort suggests that sex-related factors may play an important role in the expression or underlying mechanisms of ENM. Additionally, a correlation was found between the EEG discharge patterns and the specific limb regions involved. Regarding treatment, OXC may exacerbate ENM, necessitating cautious use. Steroid therapy should be considered for ESES cases unresponsive to ASMs. Refractory ENM with ESES warrants evaluation for structural abnormalities, particularly cortical dysplasia. Early EEG and neuroimaging improve diagnostic accuracy, while combined therapies-ASMs, immunomodulation, KD, or surgery-optimize outcomes. These findings highlight ENM's diagnostic intricacy and the need for individualized management. CLINICAL TRIAL REGISTRATION: Not applicable.