Neurophysiological signatures of hand motor response to dual-transcranial direct current stimulation in subacute stroke: a TMS and MEG study

Abstract

Background: Dual transcranial direct current stimulation (tDCS) to the bilateral primary motor cortices (M1s) has potential benefits in chronic stroke, but its effects in subacute stroke, when behavioural effects might be expected to be greater, have been relatively unexplored. Here, we examined the neurophysiological effects and the factors influencing responsiveness of dual-tDCS in subacute stroke survivors. Methods: We conducted a randomized sham-controlled crossover study in 18 survivors with first-ever, unilateral subcortical ischaemic stroke 2-4 weeks after stroke onset and 14 matched healthy controls. Participants had real dual-tDCS (with an ipsilesional [right for controls] M1 anode and a contralesional M1 [left for controls] cathode; 2 mA for 20mins) and sham dual-tDCS on separate days, with concurrent paretic [left for controls] hand exercise. Using transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG), we recorded motor evoked potentials (MEPs), the ipsilateral silent period (iSP), short-interval intracortical inhibition, and finger movementrelated cortical oscillations before and immediately after tDCS. Results: Stroke survivors had decreased excitability in ipsilesional M1 with a relatively excessive transcallosal inhibition from the contralesional to ipsilesional hemisphere at baseline compared with controls, as quantified by decreased MEPs and increased iSP duration. Dual-tDCS led to increased MEPs and decreased iSP duration in ipsilesional M1. The magnitude of the tDCS-induced MEP increase in stroke survivors was predicted by baseline contralesional-to-ipsilesional transcallosal inhibition (iSP) ratio. Baseline post-movement synchronization in α-band activity in ipsilesional M1 was decreased after stroke compared with controls, and its tDCS-induced increase correlated with upper limb score in stroke survivors. No significant adverse effects were observed during or after dual-tDCS.

Comparing different montages of transcranial direct current stimulation on dual-task walking and cortical activity in chronic stroke: double-blinded randomized controlled trial

“…Stagg et al, showed cathodal tDCS improved UE motor performance with increased activity in ipsilesional M1 as compared with sham tDCS [ 36 ]. Recently, Kuo et al showed bilateral tDCS immediately increased cortical excitability and decreased transcallosal inhibition in ipsilesional M1, with a decrease in excitability and an increase in transcallosal inhibition in contralesional M1 [ 37 ]. Our results of cathodal and bilateral tDCS on corticomotor activity in contralesional M1 were in line with Kuo et al’s study.…”

Predictive models for response to non-invasive brain stimulation in stroke: A critical review of opportunities and pitfalls

“…Finally, different assessment domains may be combined in one statistical model. A recent example originates from the study by Kuo and colleagues of subacute stroke patients (N=18) [50]. The authors assessed a set of clinical, TMS-based and magnetoencephalography-based metrics.…”

May Dual Transcranial Direct Current Stimulation Enhance the Efficacy of Robot-Assisted Therapy for Promoting Upper Limb Recovery in Chronic Stroke?

“… 9 , 15 Accordingly, the more reliable parameter to evaluate the amount of structural reserve is the presence or absence of MEP, the former being associated with more structural reserve and the latter linked to less reserve. 9 , 16 On the other hand, it has been demonstrated that tDCS can produce prolonged changes in motor cortical excitability both in healthy subjects 17 and in stroke patients, 18 resulting in MEP suppression when tDCS is delivered with cathodal montage and MEP increase when delivered with anodal montage. 19 , 20 Accordingly, tDCS has the potentiality of amending inter-hemispheric imbalance in sub-acute stroke.…”