Table 3.

Main data of the included studies

Study	Study design	Experimental conditions	Sample (N)	Stimulation site	Intensity and duration of tDCS	Number of sessions	Assessment measures	Reported results	Improvement in line bisection	Improvement in cancelation task
Turgut et al. [68]	Parallel No randomization No blinding	-Dual tDCS + Optokinetic intervention + Conventional treatment -Conventional treatment alone	32	PPC	1.5–2.0 mA 20 min	8 sessions	- Barthel Index - Body orientation on the wheelchair - Eye, head and trunk orientation (with and without cueing) - Fim/IVAR Early Rehabilitation - Line Bisection Test - The Apples Cancellation Task - The Clock Drawing Test	Combination intervention (dual tDCS + optokinetic + conventional treatment) reduces neglect for ipsilesional spontaneous body orientation and improves performance on the Clock Drawing Test compared to standard treatment	No	No
Bornheim et al. [11]	Crossover within-subjects Case Reports Randomized Double blinding	-a-tDCS + Physical therapy + Occupational therapy + Neuropsychological therapy -Sham tDCS + Physical therapy + Occupational therapy + Neuropsychological therapy	4	M1	2 mA 20 min	20 sessions	- Catherine Bergego Scale - Line Bisection Test - The Star Cancellation Test	Active tDCS improves performance in the four patients in Catherine Bergego Scale, Line Bisection Test, and The Star Cancellation Test, expressed in percentage of change, compared to sham	Yes	Yes
O'Shea et al. [57]	Crossover within-subjects 3 cases study Longitudinal Randomized No blinding	-a-tDCS + Prism adaptation -c-tDCS + Prism adaptation -Sham tDCS + Prism adaptation	3	M1	1 mA 20 min	P1: 3 active and 5 sham sessions P 2: 1 active and 1 sham sessions	-Balloons tests -Coloring, reading and filling in a mock administrative form -Copy Drawing -Letter Cancellation, star cancellation test, object cancellation (dense and sparse search array) -Line Bisection Test -Ota test -The Bells test -Percent correct scores across the tests were combined to compute the overall neglect score for each patient (6 tests for P1; 10 tests for P2 and 3)	Improvement in neglect score after M1 tDCS + prism adaptation compared to sham The improvement in neglect score lasted throughout follow-up (18–46 days)	Yes	Yes
Yi et al. [74]	Parallel Randomized No blinding	-a-tDCS + Conventional physical therapy -c-tDCS + Conventional physical therapy -Sham tDCS + Conventional physical therapy	30	PPC	2 mA 30 min	15 sessions	- Catherine Bergego Scale - Functional Ambulation Classification (basic motor skills) - K-MMSE - Korean Modified Barthel Index - Line Bisection Test - Motor-Free Visual Perception Test - The Star Cancellation Test	Improvement in motor-free visual perception test, line bisection, star cancellation, Catherine Bergego Scale, Barthel Index, and Functional Ambulation Classification in all 3 groups (a-tDCS, c-tDCS, sham) Improvements in the motor-free visual perception test, start cancellation, and line bisection were greater in a-tDCS and c-tDCS compared to sham	Yes	Yes
Bang and Bong [5]	Parallel Randomized No blinding	-tDCS + Feedback training -Feedback training alone	12	PPC	1 mA 20 min	15 sessions	- Barthel index - Line Bisection Test - Motor-Free Visual Perception Test	Improvement in Barthel index, line bisection test and motor-free visual perception test in the two groups Combined tDCS + feedback intervention show greater improvement compared to feedback training alone in all tests	Yes	Not assessed
Smit et al. [64]	Crossover within-subjects No randomized Double blinding	-Dual tDCS -Sham dual tDCS	5	PPC	2 mA 20 min	5 sessions	Behavioral Inattention Test (BIT-C): - Figure and Shape Copying - Letter Cancellation - Line Bisection Test - Line Crossing - Representational Drawing - The Star Cancellation Test	No tDCS-related effects were observed for the BIT subtests	No	No
Làdavas et al. [47]	Parallel Randomized Double blinding	-a-tDCS + Prism adaptation -c-tDCS + Prism adaptation -Sham tDCS + Prism adaptation	30	PPC	2 mA 20 min	10 sessions	Behavioral Inattention Test (BIT-C): - Figure and Shape Copying - Letter Cancellation - Line Bisection Test - Line Crossing - Representational Drawing - The Star Cancellation Test	a-tDCS PPC boosted neglect amelioration after prism adaptation c-tDCS suppresses neglect improvement after prism adaptation	Yes	Yes
Brem et al. [12]	Crossover within-subjects No randomized Double blinding	-Dual tDCS + Conventional cognitive therapy -Sham tDCS + conventional cognitive therapy	1	PPC	1 mA 20 min	6 sessions	Test for Attentional Performance: - Alertness - Covert Attention - Visual field From Neglect-Test German version of BIT: - Cancellation - Copying figures - Line Bisection Test Transfer effects on ADL	Combined intervention (dual tDCS + cognitive therapy) showed greater improvement compared to sham in cover attention, line bisection, and coping ADLs showed improvement at the 3 month follow-up	Yes	No
Sunwoo et al. [67]	Crossover within-subject Randomized Double blinding	-Dual tDCS -a-tDCS -Sham tDCS	10	PPC	1 mA 20 min	3 days Dual tDCS (1) a-tDCS (1)	- Line Bisection Test - The Star Cancellation Test	Significant improvements in line bisection after both dual and single tDCS, but not after sham, being stronger the effect after dual tDCS No significant change in star cancellation	Yes	No
Sparing et al. [66]	Crossover within-subjects No randomized No blinding	-a-tDCS contralesional PPC -c-tDCS contralesional PPC -a-tDCS lesioned PPC -Sham tDCS lesioned PPC	10	PPC	1 mA 10 min	2 days	- Line Bisection Test (computerized version) - Neglect subtest of Test Battery of Attentional Performance’ (TAP)	Both a-tDCS (ipsilesional) and c-tDCS (contralesional) improved line bisection compared to sham No significant changes were detected in neglect subtest of TAP (only a tendency of contralesional c-tDCS)	Yes	Not assessed
Ko et al. [46]	Crossover within-subjects No randomized Double blinding	-a-tDCS -Sham tDCS	15	PPC	2 mA 20 min	2 sessions	- Letter-Structured Cancellation Test - Line Bisection Test - Shape-Unstructured Cancellation Test	a-tDCS showed significant improvement in cancellation tests and line bisection tests compared to sham	Yes	Yes