Effects of primary motor cortex noninvasive brain stimulation on post-stroke aphasia: a narrative review

Table 1 Summary of M1 stimulation studies in post-stroke aphasia

Authors	Study design	Subject	Type of intervention	Session	Aphasia severity	Type of aphasia	Outcome measure	Main result
Meinzer et al. (2016) [34]	RCT	26 Chronic	Anodal tDCS (1 mA) over the left motor cortex	16	Mild	Wernicke Broca Amnestic Global	AAT	M1 tDCS enhances language recovery after stroke
Branscheidt et al. (2017) [35]	RCT	16 Chronic	Anodal tDCS (2 mA) over the left motor cortex	1	Mild	Broca Amnestic Global	AAT	Motor cortex stimulation improves lexico-semantic retrieval
Darkow et al. (2017) [36]	RCT	16 Chronic	Anodal tDCS (1 mA) over the left motor cortex	1	Mild	Amnestic	AAT	M1-tDCS enhances activity and connectivity within a naming network
Wang et al. (2018) [37]	RCT	52 Sub-acute	M1-tDCS (1.2 mA) Broca’s area	10	Moderate–severe	Broca Mixed Global	PACA BDAE	M1-tDCS improves the speech function
Stahl et al. (2019) [38]	RCT	130 Chronic	Anodal tDCS (1 mA) over the left motor cortex	15	Mild–moderate Severe	Wernicke Broca Amnestic	AAT ANELT	M1-tDCS enhances naming ability
Xu et al. (2021) [39]	Pilot	16 Sub-acute Chronic	TMS (iTBS 50 Hz, 800 pulses) over the primary motor cortex	1	Mild moderate Severe Very severe	Not applicable	WAB-AQ	M1-iTBS enhances language function and neural connectivity

AAT Aachen Aphasia Test, PACA Psycholinguistic Assessment in Chinese Aphasia, BDAE Boston Diagnostic Aphasia Examination, ANELT Amsterdam Nijmegen Everyday Language Test, WAB-AQ Western Aphasia Battery Aphasia Quotient, iTBS intermittent theta-burst stimulation, TMS transcranial magnetic stimulation, M1 primary motor cortex, tDCS transcranial direct current stimulation, RCT randomized controlled trial