Chronic pain: Pathophysiology and mechanisms

Understanding the mechanisms of pain is important for any clinician since chronic pain is a global problem that transcends all medical specialties. By understanding pain at a cellular level, clinicians can better apply multimodal pain therapies for their patients that address the four steps of pain signaling and processing: transduction , transmission , modulation , and perception . The purpose of this chapter is to explore each of these avenues along the pain pathway and examine some of the therapies currently being employed to treat pain at these levels. The chapter is divided into four sections, which comprise the four steps of the pain pathway. Within the transduction section , nociceptors and the processes by which they detect noxious stimuli are discussed. Transmission focuses on the types of nerve fibers involved in pain signaling and the differences among them. The section on modulation investigates peripheral, spinal, and supraspinal mechanisms by which "pain" transmission is modified, including peripheral and central sensitization mechanisms. Finally, perception describes the key centers of the brain responsible for pain processing and examines the influence of context and emotions.