Haptically facilitated bimanual training combined with augmented visual feedback in moderate to severe hemiplegia

Abstract

This study describes the design and feasibility testing of a hand rehabilitation system that provides haptic assistance for hand opening in moderate to severe hemiplegia while subjects attempt to perform bilateral hand movements. A cable-actuated exoskeleton robot assists the subjects in performing impaired finger movements but is controlled by movement of the unimpaired hand. In an attempt to combine the neurophysiological stimuli of bilateral movement and action observation during training, visual feedback of the impaired hand is replaced by feedback of the unimpaired hand, either by using a sagittaly oriented mirror or a virtual reality setup with a pair of virtual hands presented on a flat screen controlled with movement of the unimpaired hand, providing a visual image of their paretic hand moving normally. Joint angles for both hands are measured using data gloves. The system is programmed to maintain a symmetrical relationship between the two hands as they respond to commands to open and close simultaneously. Three persons with moderate to severe hemiplegia secondary to stroke trained with the system for eight, 30 to 60 minute sessions without adverse events. Each demonstrated positive motor adaptations to training. The system was well tolerated by persons with moderate to severe upper extremity hemiplegia. Further testing of its effects on motor ability with a broader range of clinical presentations is indicated.

Figures

Fig. 1

Experimental set-up. Top: Mirror set-up. CyberGrasp on right hand is controlled by data glove on left hand. Subject watches mirror image of his left hand to simulate observation of his right hand moving normally. Bottom: Virtual Reality set-up. Both virtual hands are controlled by movement of the unimpaired hand, showing the subject an image of their impaired hand moving normally.

Fig. 2

Graphic demonstration of the relationship between position difference between average flexion angle of the unimpaired and impaired index finger as measured by data gloves (solid gold line) and the assistive force exerted on the impaired index finger by the CyberGrasp (dashed blue line).

Fig. 3

Four consecutive repetitions collected performed by Subject One during training on Day Two. Red line is unimpaired index finger MCP angle. Blue line is impaired index finger MCP angle. Note the symmetrical position changes. Green line is the EMG signal collected at the muscle belly of the impaired hand FDS. Note the strong EMG signal during active flexion (MCP angle increasing) and the reflexive activation during passive elongation (MCP angle decreasing) of the impaired hand for each repetition.

Fig. 4

Finger position and EMG responses collected during training of Subject One. Top panel: MCP of impaired hand index finger during single opening and closing of the hand (average of 20 trials). Finger starts in full extension, closes actively, and finally is extended passively by the CyberGrasp. Bottom panel: Mean EMG response to the movement in top panel. Day 2 response (gold line) shows a strong activation during active flexion movement and a secondary burst in response to passive lengthening. On Day 6 (blue line) there is no reflex activation in response to passive lengthening.