Activity-dependent improvement of full weight-bearing standing with epidural stimulation in chronic complete paraplegics

Society for Neuroscience Chicago 2015
Spinal Cord Injury I Spinal Cord Injury and Plasticity
Support: NIH Grant R01EB007615 NIH Grant 8P30GM103507 CDRF Kessler Foundation Leona M. and Harry B. Helmsley Charitable Trust Kentucky Spinal Cord Injury Research Center University of Louisville Foundation

Activity-dependent improvement of full weight-bearing standing with epidural stimulation in chronic complete paraplegics

Abstract: Clinically complete spinal cord injury (SCI) is associated with the inability to stand or walk, and a drastic decrease in quality of life for affected individuals. The mammalian lumbosacral spinal cord can regain the ability to generate some level of weight-bearing standing after a complete SCI. Activity-dependent rehabilitation alone allowed the recovery of weightbearing standing and stepping in complete spinal cats, while its interaction with lumbosacral spinal cord epidural stimulation was needed to achieve similar results in complete rats. The aim of this study was to investigate the effects of stand training with epidural stimulation in four clinically complete SCI individuals, who were implanted with an epidural electrode array over the segments L1-S1 of the spinal cord. EMG, kinematics and ground reaction forces were recorded during standing experimental sessions performed before and after 80 stand training sessions (1 hour of standing per session, 5 days/week). Before training, all four participants needed external assistance at hips and knees to maintain upright posture, even in the presence of epidural stimulation. EMG pattern of several lower limb muscles often consisted in the alternation between EMG bursts and periods of little activity, resulting in overall unstable assisted standing. Throughout the training, epidural stimulation parameters were optimized and all participants achieved full weight-bearing standing without external assistance for knee extension. The longest knee-independent standing bout achieved by each participant was substantially different, ranging from 4.3 (participant B07) to 63.0 minutes (participant A45). After training, EMG patterns were overall more continuous, and lower levels of external assistance were needed to stand with the same stimulation parameters tested before training. However, stable standing with the least amount of assistance was achieved with individualspecific stimulation parameters optimized during training. On the other hand, without stimulation, little or no EMG activity was recorded from the analyzed muscles of all research participants, who maintained upright posture because of the trainers’ assistance at the knees and hips, and because of the weight-bearing action performed by their upper limbs. Part of the standing ability improvement after training can be explained by the enhanced motor output promoted by the reinforcement of the neural pathways directly and repetitively involved during stand training. However, the appropriate selection of stimulation parameters is critical to further improve standing after chronic complete paralysis in humans.

Disclosures: E. Rejc: None. C. Angeli: None. S. Harkema: None.

Authors: *E. REJC, C. ANGELI, S. HARKEMA; Kentucky Spinal Cord Injury Res. Ctr., Univ. of Louisville, Louisville, KY

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