Vagus Nerve Stimulation Therapy: Indications, Programing, and Outcomes

Abstract

Vagus nerve stimulation (VNS) provides palliation of seizure reduction for patients with medically refractory epilepsy. VNS is indicated for symptomatic localization-related epilepsy with multiple and bilateral independent foci, symptomatic generalized epilepsy with diffuse epileptogenic abnormalities, refractory idiopathic generalized epilepsy, failed intracranial epilepsy surgery, and other several reasons of contraindications to epilepsy surgery. Programing of the parameters is a principal part in VNS. Output current and duty cycle should be adjusted to higher settings particularly when a patient does not respond to the initial setting, since the pivotal randomized trials performed in the United States demonstrated high stimulation made better responses in seizure frequency. These trials revealed that a ≥ 50% seizure reduction occurred in 36.8% of patients at 1 year, in 43.2% at 2 years, and in 42.7% at 3 years in 440 patients. Safety of VNS was also confirmed because side effects including hoarseness, throat discomfort, cough, paresthesia, and headache improved progressively during the period of 3 years. The largest retrospective study with 436 patients demonstrated the mean seizure reduction of 55.8% in nearly 5 years, and also found 75.5% at 10 years in 65 consecutive patients. The intermediate analysis report of the Japan VNS Registry showed that 60% of 164 cases got a ≥ 50% seizure reduction in 12 months. In addition to seizure reduction, VNS has positive effects in mood and improves energy level, memory difficulties, social aspects, and fear of seizures. VNS is an effective and safe option for patients who are not suitable candidates for intracranial epilepsy surgery.

Heart‐rate variability indices as predictors of the response to vagus nerve stimulation in patients with drug‐resistant epilepsy

“…3,4 VNS has been widely accepted as an adjunctive therapy for drug-resistant epilepsy, with >115,000 devices implanted in about 80,000 patients worldwide. 5 Despite the growing application of VNS implants, the exact VNS mechanisms remain poorly understood. 6 The efficacy of VNS varies substantially due to clinical factors including epilepsy type, etiology, antiepileptic drug (AED) use, and severity of the epilepsy, and usually does not result in complete cessation of seizures.…”

Safety of high‐current stimulation for intermittent intraoperative neural monitoring in thyroid surgery: A porcine model

“…Settings may be changed as required for each patient? A comparison of high (30 seconds every 5 minutes) and low (30 seconds every 90 minutes) vagal stimulation at the setting of 30 Hz frequency and 3.5 mA current showed better reduction rate in the high‐stimulation group (50% vs. 13%) . Adverse event resulted from VNS such as hoarseness, sore throat, cough, paresthesia, and headache were not observed in daily practice during short‐term use of VNS therapy system …”

Sepsis: developing new alternatives to reduce neuroinflammation and attenuate brain injury

“…Moreover, the use of these devices was approved for drug‐resistant epilepsy and depression by the U.S. Food and Drug Administration. However, the approved stimulation parameters to trigger the activation of afferent fibers are 0.25–3.5 mA, 20–30 GHz . Different parameters should be applied to stimulate anti‐inflammatory efferent fibers.…”