Table 2.
Summary of tDCS studies in patients with fibromyalgia.
| # | Author | Design (Control Condition) |
n Active/Sham |
Mean Age ± SD | Target Electrode Site |
Return Electrode Site | Electrode Size | Intensity | Session Number and Duration | Polarity | Pain Outcome Measure | Major Finding |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Fregni et al. (2006) [28] | RCT double blind (sham controlled) | Active = 22 Sham = 11 | 53.4 ± 8.9 | Left dlPFC/ M1 |
Fp2 | 7 × 5 cm | 2 mA | 5 × 20 min | anodal | VAS/SF36-PF | Anodal tDCS of the primary motor cortex induced significantly greater pain improvement compared with sham stimulation and stimulation of the DLPFC. |
| 2 | Valle et al. (2009) [29] | RCT double blind (sham controlled) | Active = 27 Sham = 14 | 54.8 ± 9.6 | Left dlPFC/ M1 |
Fp2 | 7 × 5 cm | 2 mA | 10 × 20 min | anodal | VAS/FIQ | M1 and DLPFC stimulation both display improvements in pain scores and quality of life at the end of the treatment protocol. Only M1 stimulation resulted in long-lasting benefits at 30 and 60 follow-ups. |
| 3 | Riberto et al. (2011) [30] | RCT double blind (sham controlled) | Active = 11 Sham = 12 | 58.3 ± 12.1 | M1 | Fp2 | 7 × 5 cm | 2 mA | 10 × 20 min | anodal | SF36 (pain)/FIQ | Active treatment had a significantly greater reduction of SF-36 pain domain scores and a tendency toward higher improvement in FIQ scores as compared with sham tDCS. |
| 4 | Mendonca et al. (2011) [31] | RCT double blind (sham controlled) | Active = 24 Sham = 6 | 43.2 ± 9.8 | supra-orbital region/ M1 |
transition of the cervical and thoracic spine | 8 × 10 cm | 2 mA | 1 × 20 min (4 single sessions) | anodal/cathodal | VNS/PPT | significant pain reduction in cathodal and anodal supra-orbital region groups indexed by VNS. |
| 5 | Fagerlund et al. (2015) [32] | RCT double blind (sham controlled) | Active = 24 Sham = 24 | N/A | M1 | Fp2 | 7 × 5 cm | 2 mA | 5 × 20 min | anodal | NRS/FIQ | A small, significant improvement in pain was observed under the active tDCS but not the sham condition. Fibromyalgia-related daily functioning improved in the active tDCS group vs. the sham group. |
| 6 | Jales et al. (2015) [33] | RCT double blind (sham controlled) | Active = 10 Sham = 10 | 46.4 ± 10.61 | M1 | Fp2 | 7 × 5 cm | 1 mA | 10 × 20 min | anodal | VAS/SF36-PF | decrease in the Fibromyalgia Impact Questionnaire and the Visual Analog Scale scores in the active tDCS |
| 7 | Khedr et al. (2017) [34] | RCT double blind (sham controlled) | Active = 18 Sham = 18 | 31.3 ± 10.9 | M1 | Contralateral arm | 6 × 4 cm | 2 mA | 10 × 20 min | Anodal | VAS | Higher improvement in the experimental scores of the patients in the real tDCS group in VAS, pain threshold and depressive scores |
| 8 | To et al. (2017) [35] | RCT single blind (sham controlled) | Active = 15 Sham = 16 | 46.95 ± 10.07 | Left dlPFC/ occipital region |
O2—F4 | NR | 1.5 mA | 8 × 20 min | Anodal | NRS/PCS/MFIS | Repeated sessions of occipital tDCS improved pain, but not fatigue, whereas repeated sessions of DLPFC tDCS significantly improved pain as well as fatigue |
| 9 | Brietzke et al. (2020) [36] | RCT double blind (sham controlled) HB | Active = 10 Sham = 10 | 48.6 | Left dlPFC | F4 | 7 × 5 cm | 2 mA | 60 × 30 min | Anodal | VAS/FIQ | After the first 20 sessions of a-tDCS, the cumulative pain scores reduced by 45.65% vs. 3.94 and at the end of 60 sessions by 62.06% vs. 24.92% in active vs. sham tDCS, respectively. |
| 10 | De Melo et al. (2020) [37] | RCT double blind (sham controlled) | Active = 13 Sham = 13 | 44.81 ± 8.8 | M1 | NR | 7 × 5 cm | 2 mA | 5/10 × 20 min | Anodal | VAS/CIRS | Reduction in pain intensity after treatment for groups in general in addition to a reduction in alpha 2 oscillations in the frontal and parietal after 5 days |
| 11 | Caumo et al. (2022) [38] | RCT double blind (sham controlled) HB | Active = 32 Sham = 16 | 49.06 ± 9 | Left dlPFC | F4 | 7 × 5 cm | 2 mA | 20 × 20 min | Anodal | VAS/FIQ/PCS | a-tDCS reduced the Pain Catastrophizing Scale total scores by 51.38% compared to 26.96% in s-tDCS, and the Profile of Chronic Pain: Screen total scores by 31.43% compared to 19.15% in s-tDCS |
| 12 | Samartin-Veiga et al. (2022) [39] | RCT double blind (sham controlled) | Active = 100 Sham = 30 | 50.31 ± 8.76 | M1/dlPFC/operculo-insular cortex | Fp2 | NR | 2 mA | 15 × 20 min | Anodal | VAS/FIQ | Significant treatment effects across time for clinical pain and for fatigue, cognitive and sleep disturbances, and experimental pain |
| 13 | Loreti et al. (2023) [40] | RCT triple blind (sham controlled) | Active = 17 Sham = 18 | 41.99 ± 10.16 | M1 | Fp2 | 7 × 5 cm | 2 mA | 10 × 13 min 20 min with 13 min break | Anodal | VAS/FAS | The active tDCS group showed improvement in pain after 10, 30, and 90 days compared with the sham tDCS. Improvement in quality of life (QoL) and fatigue was observed in the active tDCS group |
| 14 | Caumo et al. (2023) [41] | RCT double blind (sham controlled) HB | Active = 68 Sham = 34 | 46.96 ± 9.42 | M1/left dlPFC | F4—Fp2 | 7 × 5 cm | 2 mA | 20 × 20 min | Anodal | FIQ/PCS | a-tDCS on DLPFC significantly reduced pain scores by 36.53% compared to 25.79% in s-tDCS. a-tDCS on M1 reduced pain scores by 45.89% compared to 22.92% over s-tDCS. |
Note: tDCS = transcranial direct current stimulation; RCT = randomized controlled trial; SD = standard deviation; dlPFC = dorsolateral prefrontal cortex; M1 = primary motor cortex; F4 = right dorsolateral prefrontal cortex; Fp2 = right supraorbital area; VAS = Visual Analogue Scale; FIQ = Fibromyalgia Impact Questionnaire; VNS = Visual Numeric Scale; PPT = Pain Pressure Threshold; PCS = Pain Catastrophizing Scale; MFIS = Modified Fatigue Impact Scale; NRS = Numeric Rating Scale; SF36 = Short-Form 36 Health Questionnaire; CIRS = Cumulative Illness Rating Scale; FAS = Fatigue Assessment Scale; HB = home-based; NR = not reported or available.