Anticonvulsive Effects of Transcranial DC Stimulation in Pharmacoresistant Focal Epilepsy

OBJECTIVES:

About 15% of patients suffering from focal epilepsy are refractory to available pharmacological treatments. Until now, the only hope for such patients has been the development of new pharmaceutical treatments or epilepsy surgery. In case of inoperability, different types of invasive brain stimulation such as vagus nerve stimulation or deep brain stimulation or non-invasive repetitive TMS have been evaluated to determine their anticonvulsive potential. For rTMS, weak and short lasting seizure reduction has been reported in different epilepsy syndromes.

A new, non-invasive stimulation technique, transcranial direct current stimulation (tDCS), was useful to modulate cortical excitability in many cortical areas (M1, visual cortex, frontal cortex). Cathodal tDCS, with a current of 1 mA, induced long-term depression in animal models and reportedly decreased the excitability of both human and animal cerebral cortex. In epilepsy patients suffering from a malformation of cortical development, a single session of cathodal tDCS helped reduce seizures briefly. The purpose of this protocol is to study the effects of repeated applications of tDCS on the excitability of the seizure focus in patients with poorly controlled pharmacologically refractory temporal lobe epilepsy.

STUDY POPULATION:

We plan to study 56 patients between the ages of 18 and 80 suffering from temporal lobe epilepsy.

DESIGN:

Subjects will be allocated by blocked randomization to one of two groups (parallel design). Group A will receive cathodal tDCS and group B will receive Sham-tDCS on five consecutive days. Each subject will participate in 9 sessions (1 baseline visit, 5 intervention visits, 3 follow-up visits). The effect of the intervention relative to the sham stimulation will be evaluated by comparing seizure frequency and neuropsychological tests during the 8 weeks before and after the intervention.

OUTCOME MEASURES:

Primary outcome measure will be the mean seizure frequency per 4 weeks in the tDCS group as compared to the Sham-tDCS group. To analyze the effect of the intervention (tDCS), seizures will be evaluated during a 2x4 week baseline period before tDCS and 2x4 weeks after the intervention. Using these data we will calculate the percentage change of seizures per 4 weeks.

Secondary outcome measures will be the scores of the neuropsychological testing (HVLT-R, BVMT-R, CTMT, COWAT) and number of epileptiform discharges in the EEG. Furthermore, th...