Fig. 1. Flow diagram of patient recruitment. The authors diagnosed 45 patients with failed back surgery syndrome. Fifteen patients of them ousted from the study because of age unsuitability or factors affecting pain sensitivity. Of the remaining 30 patients, 27 patients agreed to participate in the study. The authors also excluded 15 of the 27 patients due to depressive symptoms and lost another patient during follow-up. Finally, 11 patients were subjects for electroencephalography (EEG) analysis. Seven of them were in the effective group, and the remaining four in the ineffective group.
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