Abstract
BackgroundPercutaneous occipital nerve stimulation (ONS) is effective in refractory chronic cluster headache (rCCH) patients. Responders to ONS differ from non-responders by greater glucose metabolism in subgenual anterior cingulate cortex (sgACC). We reasoned that transcranial direct current stimulation (tDCS), a non-invasive approach, might be able to activate this area and thus improve rCCH patients. Our objective was to explore in a pilot trial the therapeutic potential of tDCS (anode at Fz, cathode over C7) and its possible effects on pain perception, frontal executive functions and mood in rCCH patients.MethodsThirty-one patients were asked to apply daily 20-min sessions of 2 mA tDCS for 4 or 8 weeks after a 1-month baseline. CH attacks were monitored with paper diaries. The primary outcome measure was change in weekly attacks between baseline and the last week of tDCS. Twenty-three patients were available for a modified ITT analysis, 21 for per-protocol analysis. We also explored treatment-related changes in thermal pain thresholds and nociceptive blink reflexes (nBR), frontal lobe function and mood scales.ResultsIn the per-protocol analysis there was a mean 35% decrease of attack frequency (p = 0.0001) with 41% of patients having a ≥ 50% decrease. Attack duration and intensity were also significantly reduced. After 8 weeks (n = 10), the 50% responder rate was 45%, but at follow-up 2 weeks after tDCS (n = 16) mean attack frequency had returned to baseline levels. The treatment effect was significant in patients with high baseline thermal pain thresholds in the forehead (n = 12), but not in those with low thresholds (n = 9). The Frontal Assessment Battery score increased after tDCS (p = 0.01), while there was no change in depression scores or nBR.ConclusiontDCS with a Fz-C7 montage may have a preventive effect in rCCH patients, especially those with low pain sensitivity, suggesting that a sham-controlled trial in cluster headache is worthwhile. Whether the therapeutic effect is due to activation of the sgACC that can in theory be reached by the electrical field, or of other prefrontal cortical areas remains to be determined.
Highlights
Percutaneous occipital nerve stimulation (ONS) is effective in refractory chronic cluster headache patients
Given the imaging results in ONS responders and the known anatomical spread of transcranial direct current stimulation (tDCS)-induced effects, we found it worthwhile to explore in a pilot-trial the therapeutic potential of anodal tDCS over the frontal cortex in refractory chronic cluster headache (rCCH), hypothesizing that it would be able to activate the subgenual anterior cingulate cortex (sgACC), i.e. the area of the brain metabolically activated in clinical responders to ONS therapy [16]
In the subgroup of patients who treated themselves with tDCS for 8 weeks (N = 10), weekly Cluster Headache (CH) attack frequency decreased from 18.90 ± 16.01 at baseline to 12.30 ± 16.57 (p = 0.041, Fig. 4)
Summary
Percutaneous occipital nerve stimulation (ONS) is effective in refractory chronic cluster headache (rCCH) patients. Non-destructive neurostimulation techniques like deep hypothalamic brain stimulation [8], occipital nerve stimulation (ONS) [9] or sphenopalatine ganglion stimulation [10] were found effective in a proportion of rCCH patients. These methods, are invasive, may cause serious adverse events [11, 12] and are not universally accessible, partly because of their high cost and need for surgical expertise [11]
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