Systematic review: Resting state functional MRI as a biomarker for non-invasive brain stimulation in upper limb recovery post-stroke.

Abstract

Background: Stroke is a leading cause of adult-onset disability. Non-invasive brain stimulation (NIBS) techniques such as transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and transcutaneous vagus nerve stimulation (tVNS) may improve arm weakness after stroke. Resting-state functional MRI (rs-fMRI) and near-infrared spectroscopy (rs-fNIRS) assess brain connectivity. Identifying the effect of NIBS on rs-fMRI/rs-fNIRS may illuminate the post-stroke recovery process. This systematic review assesses NIBS effects on clinical and rs-fMRI/rs-fNIRS outcomes in stroke survivors with arm weakness.

Methods: Systematic searches were conducted in EMBASE and MEDLINE. Articles involving adults with arm weakness from stroke, treated with more than one session of NIBS (TMS/tDCS/tVNS) and reporting clinical and rs-fMRI/rs-fNIRS outcomes at baseline and post-intervention were included. The Cochrane Risk of Bias tool was used to assess the methodological quality of included studies. Data extraction and narrative synthesis were performed.

Results: Twelve articles containing 393 participants were included. Nine studies assessed TMS, two studies assessed tDCS, and one study used dual-mode stimulation (TMS and tDCS). All studies showed significant improvements in clinical measures of arm function compared to baseline following NIBS. All studies showed changes in functional connectivity post-intervention. Enhanced interhemispheric connectivity, particularly between primary motor cortices, was positively correlated with functional outcomes.

Discussion: Both TMS and tDCS are promising adjunctive therapies for arm weakness post-stroke. Rs-fMRI, particularly interhemispheric connectivity, may provide a valid biomarker of restitution of function with NIBS. Future research should involve.