Abstracts

Rationale: To identify prospectively patients with pharmacoresistant epilepsy, who may benefit from VNS therapy. Predictive ability of tDCS should be tested. Measuring its influence on the epileptic discharges before VNS implantation should be correlated to the seizure reduction after 6 months of VNS therapy. Methods: 16 patients (age 4-17 y) with pharmacoresistant epilepsy underwent a cathodal tDCS (1 mA current, duration 15 min)over the epileptic focus 2 - 4 weeks before VNS implantation surgery. The change of epileptic discharges during 15 min scalp EEG before and after tDCS were calculated. The EEGs revealed focal, multifocal and generalized discharges. MRI pathology and seizure semiology were used additionally to define the site of tDCS, which was performed in most of the patients in the centro-temporal region. The anode was placed over the opposite hemisphere. 6 months after VNS implantation the seizure reduction was compared with the tDCS-effect on the EEG. Results: All patient suffered from psychomotor retardation and focal epilepsy with daily myoclonic, complex partial or secondary generalized seizures. They were treated with 6 to 11 antiepileptic drugs before and epilepsy surgery was not possible. 5 out of 16 patients had more than 50% seizure reduction after six months and were termed as VNS responder. Nobody became seizure free. These patients displayed a statistical significant reduction of epileptic discharges (p = .0032 Mann-Whitney U test) of -27% (median, range -12 to -36 %)versus VNS nonresponders (median 1%, range: +1 to -20%). Conclusions: The reduction of epileptic EEG discharges after a single tDCS seems to be predictive for VNS therapy outcome after 6 months. Using the tDCS tool before VNS implantation, possible VNS responders could be selected and unsuccessful VNS implantation could be avoided.