Vagus Nerve Stimulation (VNS) is recognized as an efficient procedure for controlling seizures in patients with drug-refractory epilepsies. It is used as a palliative procedure and as a complement to conventional treatment with antiepileptic (AE) drugs. According to the literature, 40 to 50 percent of patients report a decrease of at least 50 percent in seizure frequency justifying a classification as responders.

The objectives of the reported study are based on a retrospective analysis of 50 consecutive patients with partial (39) or generalized (11) refractory epilepsy who were ineligible for resective surgery. These comprised: 1 / evaluation of overall long-term effectiveness of VNS; 2 / identification of potential predictors of VNS effects on seizure frequency. No patient was seizure-free at any time in follow-up (2.8 +/- 1.8 years; max 6 years) and AE drugs therapy was maintained in all.

During follow-up 44, 66, 61, and 58 percent of patients were classified as responders at 6 months, 1, 2 and 3 years respectively. Logistic regression analysis showed that the percentage of responders at 6 months and later was significantly higher than that at earlier times (p = 0.002). Patients with generalised epilepsy did better than those with partial seizures (p= 0.03). There was a trend to better outcome in partial epilepsies symptomatic of a focal lesion than in those with a normal brain MR scan (p=0.06).

These results are in line with previously published data in terms of global efficacy and confirm that effects on seizure suppression do not attain maximal levels until at least a year after VNS. Severe generalized epilepsies (secondary or cryptogenic) manifesting as frequent falls due to atonic or tonic-clonic generalized seizures are successfully palliated by VNS and with a much lesser risk than that associated with callosotomy. The better effects of VNS in patients with partial epilepsy possibly reflect the high incidence in the reported series of developmental cortical malformations; these have been identified as one of the few variables possibly predictive of good outcome with a seizure frequency reduction of over 50 percent.

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