Vagus nerve stimulation
Vagus nerve stimulation (VNS) refers to any technique that stimulates the vagus nerve, including manual or Electrostimulation. Left cervical VNS is an approved therapy for refractory epilepsy and for treatment-resistant depression. Right cervical VNS is effective for treating heart failure in preclinical studies and a phase II clinical trial. The effectiveness of various forms of non-invasive transcutaneous VNS for epilepsy, depression, primary headaches, and other conditions has not been investigated beyond small pilot studies. The relationship between depression, inflammation, metabolic syndrome, and heart disease might be mediated by the vagus nerve. VNS deserves further study for its potentially favorable effects on cardiovascular, cerebrovascular, metabolic, and other physiological biomarkers associated with depression morbidity and mortality 1).
Vagus nerve stimulation (VNS) is an established surgical treatment for medically intractable epilepsy with more than 75 000 devices implanted worldwide till 2015.
VNS likely has a positive effect on response inhibition, at least in patients with epilepsy that benefit clinically from the treatment, presumably relating to enhancements of response-inhibition mechanisms and, therefore, identify enhanced response inhibition as a possible cognitive benefit of VNS 2).
Vagus nerve stimulation (VNS) with vagus nerve stimulator delivered during rehabilitative training enhances neuroplasticity and improves recovery in models of cortical ischemic stroke.
Rats were trained to perform an automated, quantitative measure of forelimb function. Once proficient, rats received an intrastriatal injection of bacterial collagenase to induce ICH. Rats then underwent VNS paired with rehabilitative training (VNS+Rehab; n=14) or rehabilitative training without VNS (Rehab; n=12). Rehabilitative training began ≥9 days after ICH and continued for 6 weeks.
VNS paired with rehabilitative training significantly improved recovery of forelimb function when compared with rehabilitative training without VNS. The VNS+Rehab group displayed a 77% recovery of function, whereas the Rehab group only exhibited 29% recovery. Recovery was sustained after cessation of stimulation. Both groups performed similar amounts of trials during rehabilitative, and lesion size was not different between groups.
VNS paired with rehabilitative training confers significantly improved forelimb recovery after intracerebral hemorrhage (ICH) compared to rehabilitative training without VNS 3).
Mechanism of action
Indications
Complications
Technical Aspects
see Endotracheal Tube Electrode Neuromonitoring.
The new AspireSR generator offers a unique technical improvement over the previous Demipulse. Whether the highly interesting CBSD feature will provide an additional benefit for the patients, and will rectify the additional costs, respectively, cannot be answered in the short-term. The preoperative handling is straightforward, provided that certain recommendations are taken into consideration. The intraoperative handling is equivalent to former models-except for the placement of the generator, which might cause cosmetic issues and has to be discussed with the patient carefully. We recommend the consideration of the AspireSR in patients with documented ictal tachycardia to provide a substantial number of patients for later seizure outcome analysis 4).
Outcome
Case series
An Observational study of all 43 adult patients receiving VNS for >2 years at one single center. The mean duration of treatment was 9 years. At inclusion, a semi-structured interview on VNS effectiveness was performed. In patients without benefit, the VNS was turned off. The outcome was evaluated after an observation period of one year.
21 patients (49%) reported no clear benefit and stopped VNS. Only one of them resumed treatment within one year. Patients without benefit had received more new antiepileptic drugs (AEDs) during VNS treatment than those reporting benefit (p = 0.05). Other differences between the two groups were not found. Ten patients (23%) had been seizure free >1 year at inclusion (5 in the benefit and 5 in the non-benefit group). Seizure control was attributed to the response of another new treatment in the majority of these patients.
Half of the patients had not perceived clear benefit from VNS, and all but one terminated VNS without worsening of seizures within one year. The true outcome of long-term VNS is difficult to assess in real-world practice. The effect may be overestimated due to confounding factors, particularly the common introduction of novel AEDs and the natural course of the disorder. Patients without perceived benefit from long-term VNS should not routinely remain on treatment and be subject to undue generator re-implantations 5).