Long-term outcomes of two patients with progressive myoclonic epilepsy treated with vagus nerve stimulation therapy

Abstract

PurposeLong-term outcomes associated with vagus nerve stimulation (VNS) therapy for progressive myoclonic epilepsy (PME) have not been studied. The purpose of this study was to report long-term outcomes of VNS therapy in two patients with PME. MethodsWe performed VNS therapy for two patients with PME. We reviewed the conditions of epileptic seizures, status epilepticus (SE), myoclonus, and Karnofsky performance state (KPS) scale scores at baseline and after 10 years. ResultsA 16-year-old boy with myoclonic epilepsy with ragged-red fibers (MERRF) underwent VNS therapy. Baseline KPS scale score was 50, seizure frequency was weekly, and SE occurred yearly. At 23 years old, KPS scale score was 10. He had remained SE-free and frequency of epileptic seizures had markedly reduced. At 24 years old, he died due to pneumonia. A woman with Gaucher's disease type III underwent VNS therapy at 20 years old. Baseline KPS scale score was 80, seizure frequency was daily, and SE occurred monthly. At 30 years old, KPS scale was 30. She remained SE-free, but still experienced epileptic seizures yearly. Both patients became lethargic during VNS-off periods, with symptoms improving to baseline levels when VNS was resumed. ConclusionLong-term outcomes with VNS showed good epileptic seizure control and freedom from SE. VNS might help maintain level of consciousness.