SUMMARYRegaining arm motor control is a high priority for people with cervical spinal cord injury1. Unfortunately, no therapy can reverse upper limb paralysis. Promising neurotechnologies stimulating muscles to bypass the injury enabled grasping in humans with SCI2,3 but failed to sustain whole arm functional movements that are necessary for daily living activities. Here, we show that electrical stimulation of the cervical spinal cord enabled three monkeys with cervical SCI to execute functional, three-dimensional, arm movements. We designed a lateralized epidural interface that targeted motoneurons through the recruitment of sensory afferents within the dorsal roots and was adapted to the specific anatomy of each monkey. Simple stimulation bursts engaging single roots produced selective joint movements. We then triggered these bursts using movement-related intracortical signals, which enabled monkeys with arm motor deficits to perform an unconstrained, three-dimensional reach and grasp task. Our technology increased muscle activity, forces, task performance and quality of arm movements. Finally, analysis of intra-cortical neural data showed that a synergistic interaction between spared descending pathways and electrical stimulation enabled this restoration of voluntary motor control. Spinal cord stimulation is a mature clinical technology4–7, which suggests a realistic path for our approach to clinical applications.
Anatomical organization of the lateral cervical nucleus in Artiodactyls