LAUSR

“For those who have nothing, a little is a lot.” As Sterling Bunnell, a pioneer of tetraplegic extremity reconstruction observed, small gains in function for people with spinal cord injury can equate to enormous gains in independence. People with mid-cervical spinal cord injury usually retain volitional movement at the shoulder and some control of their elbows and wrists. Hand opening and closing, a capacity that patients rate as more important to regain than walking or sexual function, is often lost. Reconstruction with tendon transfers can restore motion within the upper limbs, yet few undergo such procedures. Nerve transfers, in which expendable donor nerves are rerouted to nonfunctional recipient nerves, were developed to treat peripheral nerve and brachial plexus injuries. Donor nerve fibres grow from the transfer site along the path of the recipient nerve to reach the muscle and restore volitional motor control. Injuries to the spinal cord are neurologically complex; both upper and lower motor neurons can be damaged. In lower motor neuron paralysis, because the nerve degeneration that occurs leads to irreversible muscular atrophy, muscle reinnervation must be done within 12–18 months of injury if any function is to be restored. Conversely, in upper motor neuron paralysis, the intact lower motor neuron preserves the muscle; thus, transfers to restore volitional control in this context have no discernible time limit. Many nerve transfer options exist for spinal cord injury. In Natasha van Zyl and colleagues’ prospective case series in The Lancet, participants with upper limb paralysis due to motor level C5–C7 spinal cord injury underwent single or multiple nerve transfers in one or both upper limbs for restoration of elbow extension, grasp, pinch, and hand opening. 59 nerve transfers were completed in 16 participants (13 men and three women; 27 limbs). In ten participants (12 limbs), nerve transfers were combined with tendon transfers. In the 13 participants (22 limbs) who completed followup, improvements at 24 months versus baseline were recorded for all primary outcomes: action research arm test total score (median 34·0 [IQR 24·0–38·3] vs 16·5 [12·0–22·0], p<0·0001), grasp release test total score (125·2 [65·1–154·4] vs 35·0 [21·0–52·3], p<0·0001), and spinal cord independence measure total score (mean 39·3 [SD 13·8] vs 31·2 [7·9], greater than minimal clinically important difference). Three participants had four failed nerve transfers (Medical Research Council grade 0–1), two had a permanent decrease in sensation, and two had a temporary decrease in wrist strength that resolved by 1 year post surgery. These findings show that tendon and nerve transfers improve upper limb movement in cervical spinal cord injury, as is portrayed in the patient testimonial video for this study. As van Zyl and colleagues suggest, nerve transfers seem to restore more natural movement and finer motor control than are achieved by tendon transfers. Nerve transfers also harness existing anatomy and physiology, which circumvents risky spine-level surgery, foreign cells, complex special equipment, and implantation of devices. A single donor nerve can reinnervate multiple muscles, which is especially important in spinal cord injuries with few available donor nerves. Additionally, patients can resume light activity immediately after the procedure, avoiding the prolonged immobilisation and non-weightbearing necessary following tendon transfer. Furthermore, whereas tendon transfers can stretch out over time, results from nerve transfers improve over time through cortical plasticity. The disadvantages of nerve transfers include the months before new motion is seen and the years until full strength is achieved. van Zyl and colleagues maximised results in their patients by using the most Published Online July 4, 2019 http://dx.doi.org/10.1016/ S0140-6736(19)31332-7