Long-Term Oral Mexiletine in SCN2A-Related Epileptic Encephalopathy: A Case Report

Introduction

SCN2A-related early infantile developmental and epileptic encephalopathy is typically associated with gain-of-function variants and may respond to sodium channel blockers. Nonetheless, seizures are often refractory, and optimal management remains uncertain. We report two infants with SCN2A-related early infantile developmental and epileptic encephalopathy in whom intravenous lidocaine produced a marked antiseizure effect, enabling successful transition to long-term oral mexiletine therapy. Case Presentation: Patient 1: Frequent seizures began in the early neonatal period, with electroencephalography showing a suppression–burst pattern. Phenobarbital, midazolam, and fosphenytoin provided limited benefit. Continuous intravenous lidocaine markedly reduced seizures, and subsequent transition to high-dose oral mexiletine maintained the reduction in seizure frequency. Mexiletine therapy was continued in combination with other antiseizure medications until 3 years of age. Patient 2: Following birth asphyxia, the patient developed tonic seizures during the neonatal period. Initial improvement was achieved with phenobarbital, levetiracetam, and fosphenytoin, but seizures recurred, accompanied by a suppression–burst pattern on electroencephalography. Continuous intravenous lidocaine resulted in complete seizure cessation, followed by transition to high-dose oral mexiletine. At 3 months, infantile epileptic spasms syndrome emerged, requiring adrenocorticotropic hormone therapy, after which seizure control was maintained through 1 year of age. In both patients, serum mexiletine concentrations remained within the therapeutic range, and treatment was continued without clinically significant adverse effects.