The research reported in this thesis spans the period 1970 to 1999 and was undertaken at the Royal Victoria Hospital Belfast, Institute of Neurology and the National Hospital for Neurology and Neurosurgery, London and the University of Chicago, Chicago. In Belfast, I became interested in Head Injuries. Clinical and experimental studies demonstrated that trauma was a complex insult comprising a physical force and the physiological consequences of ischaemia and compression. These further studies carried out in London, Chicago and again London were attempts to define the importance of these factors. The benefits of early treatment of the severe head injury by controlled ventilation was established. The particular problems of compression at the foramen magnum and craniovertebral junction have occupied the last decade in London. Deformation of the neuraxis, and ischaemia are factors but here, the micromotion of the head on neck, adds a continually repeated insult akin to minor spinal cord injuries. Laterally, the embryology of the craniovertebral junction has provided new insights into compression at the craniovertebral junction. Alongside the description of the pathology has come an investigation of treatment options. A variety of surgical approaches and appropriately designed instrumentation have been devised and are now used around the World. The accumulation of clinical material over a 15 year period has provided prognostic factors in rheumatoid myelopathy, congenital malformations and skull base tumours. Taken as a whole, the studies have defined the limits beyond which the neuraxis may not function and point to methods whereby the effects of ischaemia and compression may be modified or reversed