Abstracts

Rationale: VNS has been used to treat focal and generalized epilepsy in both adults and children. Over the last years, we have tried to investigate more homogeneous patient populations that would get better results from VNS treatment. We report data from an on-going prospective study that offered VNS therapy to children with refractory secondary generalized or multifocal epilepsy who were usual candidates for callosotomy at our institution. Methods: Twenty-three kids under the age of 12 were included so far (mean= 8.4 years). Fifteent had secondary generalized (Lennox and Lennox-like syndromes) and 8 had multifocal epilepsy with generalized cortical abnormalities (tuberous sclerosis, double cortex syndrome, post-encephalitis). All were submitted to VNS. Final standard parameters were 2.5 mA, 500usec and 30Hz (30 sec on , 5 minutes off ), with progressive 0.25 mA increments every 2 weeks. Families kept a full seizure diary and neuropsychological and quality of life assessments were performed every 6 months. Mean follow-up so far is 8.6 months. Results: One kid developed stimulation-related Parkinsonism and VNS was discontinued despite a dramatic decrease in seizure frequency (80%) during therapy. The other 22 patients got at least 50% seizure frequency reduction. Seizure frequency decrease was initially noted when stimulation reached 1 mA in all patients. Attention level and cognitive improvement was noted in every kid, and did not strictly correlate with seizure outcome. All families considered that VNS had benefited their children so far. There was an immediately postoperative period (generator off ) of seizure frequency reduction ( honeymoon phase ) in 10 patients, which lasted 2-3 weeks. Four kids presented seizure frequency worsening when stimulation current was set higher then 2.5 mA. Conclusions: This patient population appeared to represent a set of patients with better seizure and cognitive outcome after VNS. Seizure frequency reduction was noted with stimulation parameters lower (1 mA) than those needed in adults and earlier during treatment. As noted with other epilepsy surgery procedures, a honeymoon phase was noted. Children might be at higher risk for seizure frequency worsening at higher stimulation currents when compared to adults.