Table 3 Intervention protocols and results in studies that targeted the motor area
Study | Polarity of target electrode | Electrode size (cm2) | Intensity (mA) Current density (mA/cm2) | Current density (mA/cm2) | Duration (min) | Number of sessions | Anatomical target (target electrode placement) | Target electrode placement | Return electrode placement | State of medication during intervention | Combined intervention | Online/offline tDCS | Adverse effects | Outcome measurements | Time points of assessment | State of medication during assessment | Results | Conclusion | Effect size (type) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Benninger et al. 2010 [50] | Anode | T = 97.5 R = 50 (two 25 cm2) | 2 0.02 | 0.02 | 20 | 8 sessions (3 times per week) | M1, SMA (8 mm anterior to Cz or forehead above eyebrows) | 8 mm anterior to Cz or forehead above eyebrows | Mastoid | On | – | Offline | Tingling | 10-m walk test | Before, 24 h, 1 and 3 months after the last tDCS intervention session | On and off | Significant decrease of walking time in off-medication state | ↑ | NR |
Costa-Ribeiro et al. 2017 [26] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 13 | 10 sessions (3 times per week) | M1, SMA (2 cm anterior to the Cz) | 2 cm anterior to the Cz | Supraorbital area of the contralateral hemisphere of the more affected side | On | Gait training associated with cues | Offline | No | 10-m walk test; TUG; cadence; stride length | Before, immediately and 1 month after intervention | On and off | 10-m walk test and TUG in 1 month after intervention | ↑ | NR |
da Silva et al. 2018 [27] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 15 | 1 | M1, SMA (1.8 cm anterior to Cz) | 1.8 cm anterior to Cz | Supraorbital area ipsilateral to the most affected side | On | Group-based exercise program | Offline | No | Gait kinematic analysis: stride length, cadence, duration, speed | Before, after | On | Gait cadence decreased | ↑ | 0.87 (Cohen’s d) |
Kaski et al. 2014 [54] | Anode | T = 10 × 4 R = 4 × 4 | 2 0.05 | 0.05 | 15 | 1 | M1, SMA (10% to 20% anterior to Cz) | 10% to 20% anterior to Cz | Inion | NR | Physical training focused on improving gait and balance or no combined intervention | Online | NR | 6-min walk; TUG; gait velocity, stride length, | Before, after | NR | Gait velocity, stride length, TUG and 6-min walk test improved in the group that received both tDCS and physical training | ↑ | 0.5 (Cohen’s d) |
Lu et al. 2018 [46] | Anode | T = medium butterfly 2.0 cc, 8.1 cm2 R = 8.5 × 6 | 1 0.12 | 0.12 | 10 | 1 | M1, SMA (1.8 cm anterior to Cz) | 1.8 cm anterior to Cz | Centrally on the forehead | NR | – | Offline | No | Center of pressure movement and force onsets in gait initiation (FoG) | Before, immediately and every 12 min. For a total of 1 h after intervention | Off | No significant change | → | NR |
Schabrun et al. 2016 [32] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 20 | 9 sessions (3 days per week) | M1 (C3) | Lt M1 | Contralateral supraorbital | On | Dual task gait training with cues | Online | Tingling | Speed, step length, cadence, TUG | 1 week before, 1 and 12 weeks after | On | No significant difference | → | NR |
Valentino et al. 2014 [53] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 20 | 5 consecutive days | M1 (C4) | Right M1 | Contralateral supraorbital | NR | – | Offline | No | Stand Walk Sit test (FoG) | Before, immediately after the 1st session, immediately, 2 days, 2 weeks and 4 weeks after 5th session | NR | Improvement in Stand Walk Sit test | ↑ | NR |
von Papen et al. 2014 [48] | Anode and cathode | T = R = 5 × 7 | 1 0.03 | 0.03 | 10 | 1 | M1 (Hotspot of first dorsal interosseus muscle) | Hotspot of first dorsal interosseus muscle | Contralateral frontal pole | NR | Transcranial magnetic stimulation with the frequency of 1 Hz | Offline | NR | Number of steps, step and stride length, cadence, double support time | Before, immediately and 30 min after stimulation | On | Improvement of number of steps, step and stride length, cadence, and double support time after anodal tDCS immediately and 30 min after stimulation | ↑ | NR |
Yotnuengnit et al. 2018 [38] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 30 | 6 sessions (3 days per week) | M1 (Cz) | Cz | Supraorbital | NR | Physical therapy focused on improving gait or no combined intervention | Offline | Burning sensation | Walking speed, step length, step width, and cadence | Before, immediately, 2, 4, and 8 weeks after intervention | NR | Similar positive outcomes in all intervention groups lasted for 8 weeks | ↑ | NR |