Pain and its treatments.

Among many relevant topics concerning pain and its treatments, the following will be considered: (1) definition of pain; (2) physiopathology; (3) methodology for clinical trials in pain research (4) use of drugs and surgical management of pain, and (5) future directions. The definition of pain as an unpleasant subjective, sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage, does not apply to living people incapable of self-report. Thus, nonverbal behavioral information is often needed and used for pain assessment. Major landmarks concerning physiopathology were: the liberation of substance P and other neuropeptides both at the spinal and peripheral endings, the anatomical and functional analysis of the nociceptive pathways, the characterization of endomorphins ligands and receptors. The difference between 'windup' and central sensitization were emphasized. Models of neuropathic pain have advanced our understanding of its specific pathophysiology. Sensoridiscriminative aspects of pain involve lateral thalamic nuclei and corresponding somesthetic cortices, whereas medial thalamic nuclei encode nociceptive stimuli during attention-directed tasks. Their cortical connections, namely anterior cingular cortex and insular cortex, support the postulate of a role in the affective-motivational dimensions of pain. An impressive increase in the number and quality of randomised clinical trials has been observed since 1950. The use of analgesics, opioids, antidepressants and other drugs is addressed, as well as new aspects concerning surgery or new drugs.