Is vagus nerve stimulation effective in the treatment of drug-resistant epilepsy?

Epilepsy is one of the most prevalent chronic neurological conditions affecting approximately 0.5–2% of the population worldwide [1] . Patients with epilepsy repeatedly and unexpectedly experience sudden changes in behavior and or consciousness. Epileptic discharges can involve only a part of the brain, causing focal seizures, or the entire brain leading to generalized seizures. First-line treatment comprises pharmacotherapy with one or more anti-epileptic drugs. Several anti-epileptic drugs are currently available with distinct mechanisms of action and side effects. However, for an estimated third of epilepsy patients, seizures remain poorly controlled despite optimal medical management. After failure of at least two anti-epileptic drugs, patients suffer from drug-resistant epilepsy. For these patients, dedicated diagnostic workup in a specialized epilepsy center is warranted and other treatment options should be explored. The most effective treatment option for patients with refractory epilepsy is epilepsy surgery. Following a thorough presurgical evaluation, seizure freedom is obtained in approximately two thirds of patients with mesial temporal lobe epilepsy and half of patients with focal neocortical epilepsy [2] . Patients who are considered unsuitable surgery candidates should be considered for neurostimulation. Several types of neurostimulation have been developed including vagus nerve stimulation (VNS), deep brain stimulation and responsive neurostimulation. Availability may differ by region. Noninvasive neurostimulation techniques are also on the rise, aiming to avoid an invasive procedure and accompanying side effects. Invasive VNS is a neurostimulation therapy which activates vagal nerve fibers in the neck region by means of a helical electrode that is wound around the cervical vagus