Clinical utility of vagus nerve stimulation for progressive myoclonic epilepsy

Progressive myoclonic epilepsy (PME) is a group of disorders in which myoclonus is a major component. Patients with PME typically have generalized tonic–clonic or clonic seizures, mental retardation culminating in dementia, and a neurologic syndrome that almost always includes cerebellar dysfunction. It comprises a heterogeneous group of inherited disorders. Conditions inwhich PME is seen include Unverricht–Lundborg disease, sialidosis, Gaucher’s disease, mitochondrial encephalomyelopathy with ragged-red fibers (MERRF), Lafora’s disease, neuronal ceroid lipofuscinosis, and Dentato-Rubro-Pallido Luysian Atrophy (DRPLA). The intensity of the various clinical features varies depending on the etiology. Although valproate, benzodiazepines, piracetam, zonisamide, topiramate, and levetiracetam have had a positive impact on the control of the epilepsy, the prognosis of this syndrome is poor. PME is also not responsive to open surgical resection. Among complimentary treatment options for epilepsy resistant tomedical and open surgical treatments, most patients so far have been treated by vagus nerve stimulation (VNS). VNS is a widely used neurostimulation for treatment-resistant epilepsy. Its components are a pulse generator and a bipolar vagus nerve lead. The generator is designed to be implanted in the patient’s chest on the upper left side. This pulse generator produces charge-balanced waveforms at a constant current. The effectiveness of VNS for PME has rarely been reported. The purpose of this study was to evaluate the efficacy of VNS for PME.