The aim of the study is to establish tDCS as a prognostic tool to predict VNS therapy outcome among patients with pharmacoresistant epilepsy.

In recent years it has been shown that many different brain stimulation techniques are effective in seizure reduction in epilepsy patients as well as in animal models of epilepsy. VNS is the method most often used with at least 45.000 patients implanted with this device worldwide. However, prediction of seizure outcome after VNS implantation is not possible in an individual patient so far. Recently, tDCS is increasingly used as a method to reduce seizure frequency in epileptic patients. Therefore it is hypothesized, that a positive effect after a single tDCS, in terms of short time seizure reduction and reduction of epileptic discharges in the EEG, could be predictive for epilepsy outcome after VNS implantation.

In the proposed multicenter prognostic study we test the predictive value of tDCS for each patient with refractory epilepsy 1 week up to 2 months before VNS implantation. The effects of tDCS will be verified via a 15 minutes long routine EEG examination, performed immediately before and after tDCS, together with seizure diary and seizure severity scale, assessed 1 month before and 1 week after tDCS. A 6 months long observation period will follow the VNS implantation. At the end of the 6 months period seizure diary and seizure severity scale of the last month will be performed to measure VNS therapy outcome. On the basis of the described variables, immediate up to 1 week long tDCS effects will be correlated to 6 months long VNS therapy outcome.

Inclusion Criteria:

• Age: 12 years and above

• At least 2 years disease history

• Refractory epilepsy:

  • Seizures are not completely responsive to longlasting antiepileptic treatment. At least 4 antiepileptic medicaments failed in mono or combined anticonvulsive regimen.
  • At least 4 seizures per week in the last month, despite adequate antiepileptic regimen.
  • Epilepsy surgery is not indicated or not accepted by the patient or by the parents of the patient.

• A stable anticonvulsive regimen, defined as unchanged dose and type of the antiepileptic medication in the last month before tDCS and before VNS implantation.

• Seizure diary is available and completed.

• VNS implantation is planned within the next 2 months.

Exclusion Criteria:

• Acute, symptomatic seizures (caused by tumor, stroke, acute encephalitis)
• Uncontrolled medical problems (e.g. cardiovascular, nephrotic oder severe, chronic or severe acute disease)
• Increased intracranial pressure for whatever reason
• Implantation of metallic material (e.g. pacemaker, cochlear-implant)
• Diseased or damaged skin over the scalp (e.g. Dermatitis)
• Pregnancy
• Known or supposed non-compliance
• Age: less than 12 years