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The physiology and morphology of thoracic spinal neurones has previously been described. This thesis now examines plasticity with respect to this population of cells in the segment rostral to a partial spinal cord injury. Intracellular penetrations were made of ventral horn interneurones, one segment rostral to an ipsilateral spinal hemisection. This was done in conjunction with extracellular recordings of expiratory bulbospinal neurones in the medulla. Spike-triggered averaging was performed to reveal new connection to the interneurones from sprouting EBSNs. The yield however, was too low to draw any valid conclusions Intracellularly penetrated interneurones were iontophoretically labelled with neurobiotin. The axons and dendritic trees were completely reconstructed. No significant difference was found overall between the control and the lesion populations in terms of numbers of collateral branches from the first 3mm of axon, although this parameter was affected by distance of the soma from the lesion and survival time. Axon collaterals terminated in a significantly larger proportion of the ventral horn/intermediate zone than in controls. This effect was significantly affected by distance from the lesion and survival time and was most prominent in the intermediate zone. These observations are taken as being indicative of axonal sprouting, although alternative hypothesis are discussed. The dendritic trees of the interneurones showed unusual features indicative of sprouting. These included tangled structures, twisted dendrites, commissural dendrites, unusually thick proximal dendrites, a lack of normal dendritic tapering, right angle branching and an overall asymmetry of the dendritic tree. Distal branches of an interneurone labelled for the cytoskeletal dendritic protein, MAP2a/b lacked immuno-labelling for this protein. Overall, MAP 2a/b labelling was noted to be less dense on the lesion side compared to the non-lesioned side of the spinal cord. Thus new forms of plasticity have been demonstrated in uninjured interneurones in the injured spinal cord.

Quantitative Sensory Testing (QST) is emerging as a potential adjunct to the neurological examination in the evaluation of sensory dysfunction after Spinal Cord injury (SCI). In both clinical and research areas, the QST technique is used as an aid in early diagnosis, follow-up, and evaluations of therapy in SCI patients. QST's are psychophysical in nature, requiring cooperation from the patient. A normative database from healthy controls helps to establish neurological disorders or changes in sensory dysfunction during the SCI treatment. A deviation from the normal range can indicate the existence of neurological disorders in Spinal cord. The main objective of this study was to establish a normative database to evaluate the sensory dysfunction after SCI and to evaluate the reliability of the QST methodology.

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.

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