Chronic pain and surgery: a review of new insights from sensory testing.

Chronic pain is increasingly recognized as an undesirable outcome after surgery. Predicting risk of postoperative chronic pain, as well as chronic pain prevention or treatment, requires understanding of the processes underlying its development. Quantitative sensory testing research over the last decade has made it possible to start understanding the alterations in central pain processing associated with chronic pain and its development. Chronic pain syndromes are typically characterized by a pronociceptive state of pain processing, e.g., generalized hyperalgesia as a sign of supraspinal central sensitization and poor inhibitory or even facilitatory descending modulation. In the perioperative context, development and progression of chronic pain are accompanied by signs congruent with a shift towards a pronociceptive state. Preoperatively, hyperalgesia and poor descending inhibitory modulation appear to increase the risk of subsequent chronic pain. Postoperatively, abnormal persistence and spread of hyperalgesia, compatible with rostral neuraxial spread of central sensitization, are increasingly linked to the development and progression of chronic pain. These findings, which need further confirmation, suggest that perioperative quantitative sensory testing of pain sensitivity and pain modulation has the potential to become a valuable clinical tool for assessing risk of chronic pain development and for managing its prevention and treatment.