Pain and its modulation. Part 1. Afferent mechanisms.

Our understanding of pain and its afferent modulation has undergone a great deal of modification in recent years as our knowledge of the sensory nervous system has expanded. In this review, current concepts are detailed in the perspective of present and potential clinical applications of basic science principles and theories to neurosurgical interventions. Beginning with peripheral receptors and fibers and traversing the peripheral nervous system to ultimately reach the central nervous system, the nociceptive information undergoes much integration and modification to affect the ultimate response of the organism to the original stimulus. At each point in the afferent pathways, various alternative neurosurgical ablative or augmentive approaches are available and might be appropriate for pain relief. For a variety of reasons many ablative procedures are being used less often in the treatment of chronic pain of a noncancerous origin, while the newer augmentive techniques are becoming more popular. On the other hand, at present ablative procedures are still used frequently for chronic pain associated with cancer, although the newer augmentive approaches are being tried in this area as well.