Brain-machine interface in chronic stroke rehabilitation: a controlled study

Abstract

Objective: Chronic stroke patients with severe hand weakness respond poorly to rehabilitation efforts. Here, we evaluated efficacy of daily brain-machine interface (BMI) training to increase the hypothesized beneficial effects of physiotherapy alone in patients with severe paresis in a double-blind sham-controlled design proof of concept study.

Methods: Thirty-two chronic stroke patients with severe hand weakness were randomly assigned to 2 matched groups and participated in 17.8 ± 1.4 days of training rewarding desynchronization of ipsilesional oscillatory sensorimotor rhythms with contingent online movements of hand and arm orthoses (experimental group, n = 16). In the control group (sham group, n = 16), movements of the orthoses occurred randomly. Both groups received identical behavioral physiotherapy immediately following BMI training or the control intervention. Upper limb motor function scores, electromyography from arm and hand muscles, placebo-expectancy effects, and functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent activity were assessed before and after intervention.

Results: A significant group × time interaction in upper limb (combined hand and modified arm) Fugl-Meyer assessment (cFMA) motor scores was found. cFMA scores improved more in the experimental than in the control group, presenting a significant improvement of cFMA scores (3.41 ± 0.563-point difference, p = 0.018) reflecting a clinically meaningful change from no activity to some in paretic muscles. cFMA improvements in the experimental group correlated with changes in fMRI laterality index and with paretic hand electromyography activity. Placebo-expectancy scores were comparable for both groups.

Interpretation: The addition of BMI training to behaviorally oriented physiotherapy can be used to induce functional improvements in motor function in chronic stroke patients without residual finger movements and may open a new door in stroke neurorehabilitation.

Copyright © 2013 American Neurological Association.

Figures

Figure 1. Brain-Machine-Interface in stroke

A) Experimental time course of the online-BMI for paralyzed chronic stroke patients’ rehabilitation. B) User wearing the 16-channel EEG system with the hand attached to the orthosis to drive extending fingers (hand opening) motions muscles as indicated by the illustration during the second part of the BMI training. The sensorimotor rhythm (SMR) power recorded from the ipsilesional electrodes (gray line) is translated into movement of the orthosis. A threshold (dashed line) calculated as the point of equal distance to the mean of the power distribution during rest (red line) and motor intention (blue line) calculated over the last 15 seconds defines rest (red shading) and motor intention (blue shading) classification areas. If the SMR power is continuously in the motor intention classification area (blue shading) for 200 msec the orthosis moves, stops if it returns to the rest classification area (red shading) for 200 msec, or maintains the previous state otherwise. The same BMI principle was applied when training reaching movements with the arm orthosis (See Supp. Info. Supp. Fig. 6). Finger extension and flexion when using hand orthosis (grasping) and upper arm extension when using arm orthosis (reaching) were part of the training task while the wrist was immobilized and fixed to the orthoses.

Figure 2. Lateralization index of BOLD activity

1 entirely contralesional; -1 entirely ipsilesional, was calculated for pre and post-training fMRI sessions during hand-opening attempt of patients with the paretic and with the healthy hand in the experimental or contingent positive group (C+) and control or sham group (S). Top: Brain activations during paretic hand movements vs. rest before and after BMI training (p