Does a therapeutic response to rTMS predict successful VNS therapy?

Background: There are no reliable criteria to identify epilepsy patients who may be especially suitable for successful vagal nerve stimulation (VNS) therapy Our hypothesis was that patients showing a clear positive response to unfocal repetitive transcranial magnetic stimulation (rTMS) might also benefit from VNS as an invasive stimulation method that effects seizure activity by widespread and diffuse impact on the impaired neuronal excitability network in epilepsy.

Method: Patients with intractable focal epilepsies were identified who had been treated in a placebo-controlled rTMS therapy study addressing unfocal 0.3 and 1.0Hz rTMS frequencies and who were treated with vagal nerve stimulation (VNS) afterwards. Seizure frequency and intensity were registered during four weeks prior to, during the one-week rTMS week and during the four weeks after rTMS. We also documented seizure frequency and intensity after onset of VNS therapy for one year including a month-by-month assessment.

Results: We found 8 patients who had participated in the rTMS trial and were supplied with a VNS afterwards (with a minimum time lag of 6 months). Three of them had been rTMS responders. Of those 2 showed no therapeutic response to VNS, the third one registered a decrease of seizure intensity and a seizure reduction by 10% with VNS. Among the 5 non-responders to rTMS 2 had a beneficial effect with VNS, one showing a temporary seizure reduction by more than 50%, the second reporting a seizure reduction by 25% and a marked antidepressant effect.

Conclusion: This pilot study does not support our hypothesis. The response to rTMS does not allow to predict promising VNS candidates.