Table 1.
Overview of the tDCS studies included in the review.
| Study | Patients features | tDCS features | Findings | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Ref | Design | MS type | Sample size (gender, age) | Pain type | Target | Protocol | Primary outcomes | Secondary outcomes | Follow up | Side effects | Results |
| Mori et al. (2010) | Randomized, parallel, double-blind sham-controlled | RR | 19 (W: 11, M: 8; age 44.8 ± 27.5) | Central NP | M1 | Five daily sessions, 2 mA, 20 min; anode: C3/C4, cathode: contralateral supraorbital area | Pain VAS, PMQ-SF | QoL (MSQOL-54), depression (BDI), anxiety (VAS) | 4 weeks | None | Pain and QoL significantly improved to active tDCS; effects lasted 3 weeks |
| Ayache et al. (2016) | Randomized, double-blind, cross-over sham-controlled | RR: 11, SP: 4, PP: 1 | 16 (W: 13, M: 3; age 48.9 ± 10.0) | NP | Left DLPFC | Three daily sessions, 2 mA, 20 min; active- sham 3 weeks washout; anode: F3, cathode: right supraorbital region | Pain VAS, BPI | Mood (HADS), attention (ANT), fatigue (MFIS) | None | Insomnia, nausea, headache (both arms), phosphene (sham) | Pain improved to active tDCS; no effect on secondary outcomes |
| Kasschau et al. (2016) | Feasibility pilot | SP: 12, RR: 6, PP: 2 (EDSS: 1–8) | 20 (W: 17, M: 3; age 51 ± 9.25) | NS | Left DLPFC | Ten remotely supervised tDCS sessions, 20 min and cognitive rehabilitation; uniform bilateral DLPFC (left anodal) montage | Completion of at least 8 tDCS sessions | Pain (PROMIS, VAS), fatigue (PROMIS, VAS), affect (PANAS), cognitive speed (ANT-I) | None | None relevant | Nineteen patients completed 8 tDCS sessions; all outcomes consistently improved |
| Rudroff et al. (2019) | Case report | RR | 1 (M, 52 years) | NP | Left M1 | Five daily sessions, 2 mA, 20 min; anode: C3, cathode: contralateral supraorbital area | Pain VAS, NPSI | [18F]-FDG PET | None | None | Pain improved and [18F]-FDG PET uptake increased in the thalamus after tDCS |
| Workman et al. (2020) | Randomized, double–blind sham-controlled cross-over pilot | RR | 6 (W: 3, M: 3; age 46.7 ± 14.1) | NS | M1 | Five daily sessions, 2 mA, 20 min; anode: C3/C4, cathode: contralateral supraorbital area | Pain VAS, fatigue (FSS), depression (BDI) | Isokinetic leg strength, fatigability testing | None | None | Pain, fatigability and fatigue improved to active tDCS |
ANT, Attention Network Test; ANT-I, Attention Network Test-Interaction; BDI, Beck Depression Inventory; BPI, Brief Pain Inventory; DLPFC, dorsolateral pre-frontal cortex; EDSS, Expanded Disability Status Scale; [18F] FDG-PET, [18F] fluorodeoxyglucose positron emission tomography; FSS, Fatigue Severity Scale; HADS, 14-item Hospital Anxiety and Depression Scale; M, men; mA, milliampere; MFIS, Multidimensional Fatigue Inventory Score; MPQ-SF, McGill pain questionnaire short form; MS, multiple sclerosis; MSQOL-54, Multiple Sclerosis Quality of Life-54 scale; M1, primary motor cortex; NP, neuropathic pain; NPSI, Neuropathic Pain Symptom Inventory; NS, not specified; PANAS, Positive and Negative Affect Schedule; PP, primary progressive; PROMIS, Patient Reported Outcomes Measurement Information System; QoL, quality of life; Ref, reference; RR, relapsing remitting; SP, secondary progressive; tDCS, transcranial direct current stimulation; VAS, Visual Analog Scale; W, women.