Root repair review: basic science background and clinical outcome.

Spinal nerve root injuries have a profound effect on the different parts (PNS and CNS) of the root itself as well as the pertinent spinal cord segment. A root avulsion from the spinal cord is a longitudinal spinal cord injury. There is degeneration of sensory and motor axons, loss of synapses, deterioration of local segmental connections, nerve cell death and reactions among non neuronal cells with scar formation, i.e. a cascade of events similar to those known to occur in any injury to the spinal cord. For function to be restored, nerve cells must survive and there must be regrowth of new nerve fibres along a trajectory consisting of CNS growth-inhibitory tissue in the spinal cord as well as PNS growth-promoting tissue in nerves. Problems in PNS regeneration such as non directional growths and unspecific reinnervation of target organs lead to unpredictable sensorimotor activity and conspires against a useful recovery of function. From the results of basic science experiments, a surgical strategy to treat root avulsion with spinal cord injury has been developed. In humans this technique is currently the most promising treatment of any spinal cord injury, with return of useful function together with pain alleviation in cases where all nerves to the extremity have been avulsed from the spinal cord. At present the shortcomings of this technique are proportionate to the delay before surgery, which leads to death of nerve cells and incomplete and unpredictable recovery. In order to improve this situation and achieve further recovery of useful function including sensory perceptions and to fully alleviate pain it is necessary to pursue research and development of both basic and clinical science.