Iron 'ElectriRx' man: Overground stepping in an exoskeleton combined with noninvasive spinal cord stimulation after paralysis

Abstract

We asked whether coordinated voluntary movement of the lower limbs could be regained in an individual having been completely paralyzed (>4 yr) and completely absent of vision (>15 yr) using a novel strategy - transcutaneous spinal cord stimulation at selected sites over the spinal vertebrae with just one week of training. We also asked whether this stimulation strategy could facilitate stepping assisted by an exoskeleton (EKSO, EKSO Bionics) that is designed so that the subject can voluntarily complement the work being performed by the exoskeleton. We found that spinal cord stimulation enhanced the level of effort that the subject could generate while stepping in the exoskeleton. In addition, stimulation improved the coordination patterns of the lower limb muscles resulting in a more continuous, smooth stepping motion in the exoskeleton. These stepping sessions in the presence of stimulation were accompanied by greater cardiac responses and sweating than could be attained without the stimulation. Based on the data from this case study it appears that there is considerable potential for positive synergistic effects after complete paralysis by combining the overground stepping in an exoskeleton, a novel transcutaneous spinal cord stimulation paradigm, and daily training.

Figures

Figure 1:

Mean EMG activity (30 consecutive steps) from the RF and soleus muscles during a normalized step cycle with and without stimulation at T11 and T11+Co1 during active (with voluntary effort) and a passive (without voluntary effort) mode.

Figure 2:

A) mean±SD(30 steps) iEMG from the RF and soleus muscles while stepping in the EKSO. B) mean±SD assistance provided by the EKSO during stepping under different conditions. C) mean±SD current drawn by the knee motor while stepping in the EKSO under different conditions.

Figure 3:

Bandpass filtered EMG with the subject in supine position while attempting to flex the left knee with and without stimulation at T11 and/or Co1.