Vagus nerve stimulation (VNS) was approved by the US FDA in 1997 as an adjunctive treatment for medically
refractory epilepsy. It is considered for use in patients who are poor candidates for resection or those in whom resection
has failed. However, disagreement regarding the utility of VNS in epilepsy continues because of the variability
in benefit reported across clinical studies. Moreover, although VNS was approved only for adults and adolescents
with partial epilepsy, its efficacy in children and in patients with generalized epilepsy remains unclear. The authors
performed the first meta-analysis of VNS efficacy in epilepsy, identifying 74 clinical studies with 3321 patients suffering
from intractable epilepsy. These studies included 3 blinded, randomized controlled trials (Class I evidence); 2
nonblinded, randomized controlled trials (Class II evidence); 10 prospective studies (Class III evidence); and numerous
retrospective studies. After VNS, seizure frequency was reduced by an average of 45%, with a 36% reduction in
seizures at 3–12 months after surgery and a 51% reduction after > 1 year of therapy. At the last follow-up, seizures
were reduced by 50% or more in approximately 50% of the patients, and VNS predicted a ≥ 50% reduction in seizures
with a main effects OR of 1.83 (95% CI 1.80–1.86). Patients with generalized epilepsy and children benefited significantly
from VNS despite their exclusion from initial approval of the device. Furthermore, posttraumatic epilepsy and
tuberous sclerosis were positive predictors of a favorable outcome. In conclusion, VNS is an effective and relatively
safe adjunctive therapy in patients with medically refractory epilepsy not amenable to resection. However, it is important
to recognize that complete seizure freedom is rarely achieved using VNS and that a quarter of patients do not
receive any benefit from therapy. (DOI: 10.3171/2011.7.JNS11977