Deafferentation and causalgia.

The concept of deafferentation pain has been developed as an entity distinct from somatic pain which can arise in the course of both cancerous and nonmalignant disease. Its distinctive clinical features and responses to diagnostic and therapeutic manipulations have been reviewed. Evidence is marshalled to show that it results from gradually developing alterations in the central nervous system, which, once established, persist despite removal of the original stimulus. Evidence is presented that the mesencephalic tegmentum may be part of a reticulothalamocortical system undergoing denervation hypersensitivity following deafferentation, whose stimulation by electric impulses, and, presumably, naturally occurring neural inputs, can result in a painful conscious experience reproducing the patient's pain in a manner similar to that whereby stimulation of temporal-parietal association cortex elicits recall of past events.