Anodal transcranial direct stimulation (tDCS) targeting the anterior cingulate gyrus for the preventive treatment of chronic cluster headache: a proof of concept trial.

Background
There is a need for better treatments in chronic cluster headache (CCH). In responders to percutaneous occipital nerve stimulation, the subgenual anterior cingulate gyrus (sACG) was found hypermetabolic (Magis et al. 2011). We reasoned that activation of this area by transcranial neurostimulation could be effective in CCH.
Aim
To explore the preventive effect of anodal (i.e. activating) transcranial direct current stimulation (tDCS) targeting the anterior cingulate gyrus in CCH patients.
Method & subjects
Difficult-to-treat CCH patients with a stable preventive drug regimen applied tDCS (2mA) interictally in 20-minute daily sessions for 4 weeks with the anode positioned over the forehead (FpZ), the cathode over the C7 spinous process. Therapeutic effects were monitored with paper diaries.
Results
Nineteen patients were enrolled up to now. In 13 patients who completed the trial, mean weekly attack frequency decreased by 38% after 4 weeks of daily stimulation (W-test: p = 0.002). The 50% responder rate was 54%. Patients (n=12) reported an improvement in headache impact, as shown by 5-point decrease in the mean HIT-6 score (from 67 to 62, p = 0.02). In 10 patients who were followed up after the treatment period, the benefit remained stable up to 4 weeks after the last stimulation.
The first 3 enrolled patients had superficial skin burns under the adhesive cathode electrode. Sponge electrodes were therefore used in all subsequent patients without any adverse effect.
Conclusion
Anodal tDCS targeting the anterior cingulate gyrus seems promising for the preventive treatment of chronic cluster headache as suggested by this ongoing proof-of-concept trial. Use of adhesive electrodes is not recommended.