Non-invasive brain stimulation in limb praxis and apraxia: A scoping review in healthy subjects and patients with stroke.

Non-invasive brain stimulation (NIBS) techniques are widely used in research settings to investigate brain mechanisms and increasingly being used for treatment purposes. The aim of this study was to systematically identify and review the current literature on NIBS studies of limb praxis and apraxia in healthy subjects and stroke patients with a scoping review using PRISMA-ScR guidelines. MEDLINE-PubMed, EMBASE and PsycINFO were searched. Inclusion criteria were English peer-reviewed studies focusing on the investigation of limb praxis/apraxia using repetitive transcranial magnetic stimulation (rTMS), or transcranial direct current stimulation (tDCS). Fourteen out of 139 records met the inclusion criteria, including thirteen studies with healthy subjects and one with stroke patients. The results of our systematic review suggest that in healthy subjects NIBS over left inferior parietal lobe (IPL) mainly interfered with gesture processing, by either affecting reaction times in judgment tasks or real gesturing. First promising results suggest that inhibitory continuous theta burst stimulation (cTBS) over right IPL may enhance gesturing in healthy subjects, explained by transcallosal facilitation of left IPL. In stroke patients, excitatory anodal tDCS over left IPL may improve limb apraxia. However, larger well powered and sham-controlled clinical trials are needed to expand on these proof-of-concept results, before NIBS could be a treatment option to improve limb apraxia in stroke patients.