Optimizing recovery potential through simultaneous occupational therapy and non-invasive brain-stimulation using tDCS

Abstract

Purpose: It is thought that following a stroke the contralesional motor region exerts an undue inhibitory influence on the lesional motor region which might limit recovery. Pilot studies have shown that suppressing the contralesional motor region with cathodal transcranial Direct Current Stimulation (tDCS) can induce a short lasting functional benefit; greater and longer lasting effects might be achieved with combining tDCS with simultaneous occupational therapy (OT) and applying this intervention for multiple sessions.

Methods: We carried out a randomized, double blind, sham controlled study of chronic stroke patients receiving either 5 consecutive days of cathodal tDCS (for 30 minutes) applied to the contralesional motor region and simultaneous OT, or sham tDCS+OT.

Results: we showed that cathodal tDCS+OT resulted in significantly more improvement in Range-Of-Motion in multiple joints of the paretic upper extremity and in the Upper-Extremity Fugl-Meyer scores than sham tDCS+OT, and that the effects lasted at least one week post-stimulation. Improvement in motor outcome scores was correlated with decrease in fMRI activation in the contralesional motor region exposed to cathodal stimulation.

Conclusions: This suggests that cathodal tDCS combined with OT leads to significant motor improvement after stroke due to a decrease in the inhibitory effect that the contralesional hemisphere exerts onto the lesional hemisphere.

Fig. 1

Brain model of altered interhemispheric inhibition in patients with a unihemispheric stroke and the therapeutic options to ameliorate this imbalance. The balance of interhemispheric inhibition becomes disrupted after a stroke (A), such that the healthy hemisphere exerts an unopposed inhibitory influence onto the lesional hemisphere and possibly interferes in the recovery process. There are three possible ways to ameliorate this process by non-invasive brain-stimulation with tDCS: the excitability in the affected (lesional) hemisphere is upregulated through anodal tDCS (B), the excitability in the unaffected (normal) hemisphere is down regulated through cathodal tDCS (C) or a combination of B and C is applied. In the current study, we tested the efficacy of option C.

Fig. 2

Absolute UE-FM scores at baseline and 1 week after the 5-day intervention. The bar graph shows the significantly (*) higher changes in the cathodal tDCS+OT group compared to the sham tDCS+OT group.

Fig. 3

FMRI activation pattern of a motor task in a stroke patient before and after cathodal tDCS applied to the contralesional hemisphere. FMRI study of paced wrist flexion and extension movements before (Fig. 2a) and after (Fig. 2b) 5 days of cathodal tDCS+OT. It has been shown that the ipsilateral (to the moving hand) sensorimotor cortex can become active when a patient performs a flexion and extension movement with the recovering wrist. Applying cathodal stimulation to the nonlesional motor cortex – the left hemisphere in this patient - significantly decreased this activation and was associated with an improvement in this patient’s functional motor status. There was also an increase in activation in the motor region of the lesional hemisphere (right hemisphere) in this patient. However, this effect was seen in some patients, but was not significant across the entire group. Functional images are thresholded at p < 0.05 (FWE corrected).

Fig. 4

Correlation of improvement in UE-FM and change in activation in the contralesional motor cortex. There was a strong trend for an inverse correlation between a greater decrease in contralesional motor cortex activation and a larger improvement in UE-FM scores after the 5-day intervention. Patients in the cathodal tDCS+OT group are marked in blue and patients in the sham tDCS+OT group are marked in red.