The role of spinal cord plasticity after birth injury and recovery from obstetric brachial plexus lesions was investigated in newborn rats with selective crush injury to spinal roots C5 and C6, in a study at University Clinics of Vienna School of Medicine, Austria. Evaluation of recovery of function following motoneuron loss, using the Bertelli test of grooming, grid walk, retrograde tracing of motoneuron pools, and functional muscle testing, showed that the adjacent C7 motoneuron contribution to biceps muscle innervation increased 4-fold after upper trunk lesions, compensating for the motoneuron loss from injury. 
COMMENT. In newborns with obstetric brachial plexus palsy affecting spinal roots C5 and C6, an intact C7 innervation of the biceps muscle is essential for a recovery process to ensue. The loss of motoneurons in C5 and C6 spinal cord segments is compensated for by changes in the spinal cord architecture and an increased contribution of C7 motoneurons.