Neurophysiologic and pathologic aspects of acute and chronic pain.

Acute pain produced by disease or injury is the net effect of highly complex interactions of various neural systems and psychological factors. Through the interaction of the afferent systems and neocortical processes, the individual is provided perceptual information regarding location, magnitude, and spatial and temporal properties of the noxious stimulus that activates motivational tendencies toward escape or attack and permits analysis of multimodal information, past experience, and probability of outcome of different response strategies. In contrast, chronic pain is a malefic force that taxes the physical, emotional, and economic resources of the patient, his famiily, and society. Moreover, chronic pain is characterized by physiological affective and behavioral responses that are quite different than those of acute pain. The clinician must keep these differences in mind in order to provide patients with optimal relief of their pain.