Vagus nerve stimulation in the treatment of patients with pharmacoresistant epilepsy: our experiences
Vagus nerve stimulation (VNS) for the treatment of refractory partial epileptic seizures with or without secondary generalisation in patients older than 12 years was approved in Europe in 1994 and in the United States in 1997. We have studied the efficacy of VNS in patients with pharmacoresistant epilepsy hospitalized in the Neurology Department of the University Hospital Centre Zagreb. From 1997 to 2001 we have implanted VNS in 11 patients with pharmacoresistant epilepsy, who were magnetic resonance imaging (MRI) negative and from May 2007 to May 2009 in 11 patients with pharmacoresistant epilepsy, 9 of them were MRI positive, and were inoperable due to localisation of the pathomorphologic changes (ganglioglioma, hamartoma, various types of cortical dysplasia, porencephalic cysts), 2 were MR negative. In the group of MRI negative patients 1 patient had complex partial seizures (CPS), 6 patients had CPS with secondary generalisation, 2 patients had primary generalized epilepsy (PGE) including myoclonic, absence, atonic and tonic-clonic seizures, one patient had PGE and CPS, and 3 patients had Lennox-Gastaut syndrome (LGS). In the group of MRI positive patients one patient had elementary partial seizures (EPS) and CPS, two patients had EPS and CPS with secondary generalisation, one patient had CPS, 3 patients had CPS with secondary generalisation, and 2 patients had CPS with secondary generalisation as well as atonic seizures. After continuous follow-up of 11 MRI negative patients during 5 years and 2 MRI negative patients during one year there was decrease in mean-seizure frequency of 51.67%. After continuous follow-up of 9 MRI positive patients during 2 years there was decrease in mean-seizure frequency of 61.9%. The most frequent side effects were hoarseness, throat pain and cough in the "on phase" of the VNS, but they were mild and transitory. We can conclude that VNS was effective mode of therapy in our group of patients with pharmacoresistant epilepsy.