Abstract
Epilepsy as a common neurological disease is mostly managed effectively with antiepileptic medications. One-third of patients do not respond to medical treatments requiring alternative therapies. Vagus nerve stimulation (VNS) has been used in the last decades for the treatment of medically resistant epilepsy. Despite the extensive use of VNS in these patients, factors associated with clinical outcomes of VNS remain to be elucidated. In this study, we evaluated factors affecting VNS outcomes in epileptic patients to have a better understanding of patients who are better candidates for VNS therapy. Several databases including PubMed, Scopus, and Google Scholar were searched through June 2020 for relevant articles. The following factors were assessed in this review: previous surgical history, age at implantation and gender, types of epilepsy, duration of epilepsy, age at epilepsy onset, frequency of attacks, antiepileptic drugs, VNS parameters, EEG findings, MRI findings, and biomarkers. Literature data show that nonresponder rates range between 25% and 65%. Given the complexity and diversity of factors associated with response to VNS, more clinical studies are needed to establish better paradigm for selection of patients for VNS therapy.
Highlights
Epilepsy is one of the most prevalent neurological conditions involving nearly one percent of the world population
It is speculated that the structural changes consequent to surgical interventions in the brain may play some critical roles in response to treatment for epileptic patients
Kawai et al emphasized that previous resective surgery and residual pathology do not influence the efficacy of vagus nerve stimulation (VNS) in treatment of epilepsy [10]
Summary
Epilepsy is one of the most prevalent neurological conditions involving nearly one percent of the world population. E quest for identification of treatments for neurologic disorders and brain abnormalities have led to the development of a treatment method called vagus nerve stimulation (VNS). VNS which consists of chronic, intermittent stimulation of vagus nerve (usually left side) has been approved by FDA [1, 3, 4] for treatment of partialonset, drug-resistant epileptic patients who are not suitable candidates for curative surgical resection or patients in whom resective surgery has provided no benefit. Being initially approved for patients with 12 years of age and older, investigations of recent decades have shown that VNS is a safe and effective method for adults and children of all ages suffering from different types of epileptic disorders [6, 7]. Low morbidity and sustained therapeutic effects of VNS have been mentioned as advantages of this treatment. [8]
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