In this work, the functional consequences of segmental spinal cord regeneration and plasticity after spinal cord nerve root injury and repair in humans were studied. Spinal nerve root avulsions occur particularly in brachial plexus traction injuries. Models of spinal cord regeneration and functional recovery in patients with spinal root avulsion were developed and changes in motor, sensory and autonomic functions in patients with severe brachial plexus injury studied with clinical and neurophysiological techniques. Regeneration of long fibre tracts and /or segmental connections was assessed. Patients were recruited at RNOH, Stanmore, and patient studies performed at the Hammersmith Hospital. Fifty one patients who had sustained, total brachial plexus injury with spinal nerve root avulsion repaired by various surgical strategies were assessed for recovery of motor function and motor phenomena (co-contraction and "breathing arm"). The results demonstrate that, following re-connection of avulsed spinal roots to the spinal cord, injured motor neurons can regenerate from the CNS to the periphery with functional recovery. The outcome was similar to that for conventional repair of a less severe brachial plexus injury. Seventy six patients who had sustained brachial plexus injury were studied for sensory and pain phenomena at different time points after injury. Pain was assessed by direct interview using pain questionnaires. Different sensory modalities in affected dermatomes showed very poor or no recovery. This study concluded that, due to the complexity of the sensory system, recovery of sensory function depends not only on technically successful nerve repair but also on CNS plasticity. It was found that patients without any surgical repair suffered the worst pain and its severity is least in the patient group repaired by graft or other nerve transfer.