Changes in Trunk independence following Stand Training with spinal cord epidural stimulation in Cervical SCI: Two Case Studies

Most individuals with motor complete spinal cord injury are unable to stand independently without external assistance. Activity Based Recovery Training (ABRT) promotes reactivation of the neuromuscular system below the level of injury. In addition, spinal cord epidural stimulation (scES) allows for the integration of sensory information leading to the modulation of motor output in the lower extremities. We present a comparison of two case studies proving evidence of the progression of recovery of trunk control during standing with scES and the reliance on upper limb support during standing. One individual (C3 AIS-A) was able to regain independent trunk control and recovered some ability to stand without upper extremity support when assisted at the hips. The second individual (C4 AIS-A) had shorter bouts of trunk independence and always required upper extremity support. Both individuals received 2 hours of stand ABRT with scES for 160 sessions. Participants were assessed prior to the start of training (pre-intervention), after 80 sessions (post intervention 1) and after 160 sessions (post intervention 2). Both participants required trunk assistance in addition to upper limb support to maintain proper trunk kinematics at the pre-intervention time point. This was illustrated by lower forces with a lower coefficient of variation (c.v.) generated through upper extremities compared to periods of independent trunk with upper extremity support. The individual that achieved the greatest level of trunk independence, average of 52 min during intervention 1 and 98 mins during intervention 2, showed a reduction in vertical forces placed through the upper extremities and a reduction in the c.v. when comparing post intervention 2 to post intervention 1. In contrast, the individual with an average of 22 min and 30 min of trunk independence across training sessions during intervention 1 and 2 respectively, showed limited difference in vertical upper extremity force and c.v. at both time points. Results from this investigation demonstrate the ability to improve trunk control following standing ABRT with scES and decrease the reliance on upper extremity support to maintain proper trunk posture in individuals with a cervical motor complete injury. We show that increased trunk independence time has a tendency to reduce the amount of upper extremity support, hinting towards increased activation of trunk musculature for proper posture. Hereby providing evidence that scES modulates network excitability of the injured spinal cord leading to integration of afferent input to activate trunk and lower extremity muscles and improve independence during stable standing.