The 'dying back' process. A common denominator in many naturally occurring and toxic neuropathies

The "dying back" process can be defined as a pathological changes affecting certain neurons in a number of systematized degenerative conditions. Examples exist to illustrate the nature of this process, which is unique to nervous tissue, and there is an association of this process with certain chronic vitamin-deficiency syndromes and some important neurotoxic chemicals. Albeit largely speculative, one can attempt to group the conditions showing the dying back process in terms of putative metabolic lesions. Although this attempt is admittedly only a first approximation, it enables us to look ahead to a future understanding of the metabolic problems of long neurons and how their selective degeneration comes about.