Effectiveness of a combined transcranial direct current stimulation and virtual reality-based intervention on upper limb function in chronic individuals post-stroke with persistent severe hemiparesis: a randomized controlled trial

Abstract

Background: Functional impairments derived from the non-use of severely affected upper limb after stroke have been proposed to be mitigated by action observation and imagination-based techniques, whose effectiveness is enhanced when combined with transcranial direct current stimulation (tDCS). Preliminary studies in mildly impaired individuals in the acute phase post-stroke show intensified effects when action is facilitated by tDCS and mediated by virtual reality (VR) but the effectiveness in cases of severe impairment and chronic stroke is unknown. This study investigated the effectiveness of a combined tDCS and VR-based intervention in the sensorimotor function of chronic individuals post-stroke with persistent severe hemiparesis compared to conventional physical therapy.

Methods: Twenty-nine participants were randomized into an experimental group, who received 30 minutes of the combined tDCS and VR-based therapy and 30 minutes of conventional physical therapy, or a control group, who exclusively received conventional physical therapy focusing on passive and active assistive range of motion exercises. The sensorimotor function of all participants was assessed before and after 25 one-hour sessions, administered three to five times a week, using the upper extremity subscale of the Fugl-Meyer Assessment, the time and ability subscales of the Wolf Motor Function Test, and the Nottingham Sensory Assessment.

Results: A clinically meaningful improvement of the upper limb motor function was consistently revealed in all motor measures after the experimental intervention, but not after conventional physical therapy. Similar limited effects were detected in the sensory function in both groups.

Conclusion: The combined tDCS and VR-based paradigm provided not only greater but also clinically meaningful improvement in the motor function (and similar sensory effects) in comparison to conventional physical therapy.

Keywords: Eye-tracking; Hemiparesis; Stroke; Surface electromyography; Transcranial direct current stimulation; Virtual reality.

Fig. 1

Virtual environment of the self-triggered motor observation task. The self-triggered motor observation task simulated an apple-picking task in an apple orchard (a). If interaction was successful, an animation showed the left or right virtual arm extending towards the apple (b), grasping it (c), bringing it towards the mouth (d), biting it several times (e), and moving the arm to the initial position. The figure represents an animation sequence with the right hand

Fig. 2

Experimental setup. Participants sat in a chair with their arms on a table, upon which a laptop was located. The intervention provided visual and auditory stimulation through the screen (a) and speakers (b) of the laptop, respectively, vibrotactile feedback through three independent vibrators (c), and transcranial direct current stimulation (d). Interaction was allowed through gaze, detected by a portable eye-tracking bar (e) and muscular activity and movement, detected by the gyroscopes, accelerometers, and/or surface electromyographic activity of a motion control armband (f)

Fig. 3

CONSORT flow diagram. Progress through the phases of the parallel randomized trial of both groups