Event related desynchronization-modulated functional electrical stimulation system for stroke rehabilitation: a feasibility study

Abstract

Background: We developed an electroencephalogram-based brain computer interface system to modulate functional electrical stimulation (FES) to the affected tibialis anterior muscle in a stroke patient. The intensity of FES current increased in a stepwise manner when the event-related desynchronization (ERD) reflecting motor intent was continuously detected from the primary cortical motor area.

Methods: We tested the feasibility of the ERD-modulated FES system in comparison with FES without ERD modulation. The stroke patient who presented with severe hemiparesis attempted to perform dorsiflexion of the paralyzed ankle during which FES was applied either with or without ERD modulation.

Results: After 20 minutes of training, the range of movement at the ankle joint and the electromyography amplitude of the affected tibialis anterior muscle were significantly increased following the ERD-modulated FES compared with the FES alone.

Conclusions: The proposed rehabilitation technique using ERD-modulated FES for stroke patients was feasible. The system holds potentials to improve the limb function and to benefit stroke patients.

Figure 1

Schematic of the experimental system.a: Active electrode system, 3 filled circles: positions of EEG electrodes. b: Wireless multi-telemeter system, b1: sender, b2: receiver. c: Computer with A/D-D/A converter. d: Electrical stimulator and isolator for FES. e: The filled square presented as a cue during the task period. The 8-steps bar height denoted the FES amplitude intensity.

Figure 2

Temporal sequence of ERD.a: An example of ERD appearance. The ERD appearance was determined every 500 ms in the intervention experiment. b: An example of stimulation sequence in the intervention experiment, which is modulated by ERD appearance shown in (a). The amplitude of stimulation intensity changed dependent on the ERD appearance. When the amplitude reached the maximum step, the current was returned to zero (arrow). c: An enlarged view of (b). The amplitude of current pulse train (50 Hz rectangle pulses; 1.2 ms width) was modulated. d: For FES training without ERD (control experiment), the stimulation sequence consisting of two trapezoidal forms was used.

Figure 3

EMG and maximum angle range of motion.a: Mean of peak EMG in post-training which was normalized to pre-training. b: Mean of maximum range of motion of the paretic ankle after the training. Error bars: SD. Asterisk: p < .001. Black bar: intervention experiment (ERD modulated FES). Gray bar: control experiment.