[Anatomic-physiologic principles of pain].

Pain, particularly chronic pain, arises from the interaction of multiple simultaneously operating physiologic processes. The current understanding of the anatomy and physiology of pain is limited to a characterization of pathways and does not explain why a particular stimulus is felt as pain of a particular kind and intensity. In this article, we trace the afferent pain pathways from periphery (reception) to center (perception), i.e., from peripheral nerve, through the spinal cord and brain stem, to the thalamus and cerebral cortex. A number of neurosurgical procedures for the treatment of pain are discussed, and their anatomic basis is explained.