Mechanisms of clinical pain. Observations and speculations

Advances in basic research have provided extraordinary insights into the physiologic systems subserving pain transmission and modulation. Although these data can provide a foundation for the understanding of clinical pain, the relationship between clinical phenomena and the diverse findings of studies performed in animal and human models of experimental pain is often obscure. A classification of pain pathophysiology is proposed in an effort to clarify this relationship. Within this classification, the data that elucidate the mechanisms of specific pain-related phenomena observed in the clinical setting are reviewed.