Historical background of the evaluation of pain in humans

The evaluation of pain in humans is a key element to plan an adequate analgesic treatment. However, the implementation of such measures was only attained in the early XX century. After the psychophysical approach of the first researchers, reliable pain evaluation was reached using the methodology of clinical trials and the use of specific questionnaires only fifty years ago. Modern analgesiometry is essentially based in the application of self-evaluation methods which were developed in the 1960s and 1970s by Anglo-Saxon researchers. In the last years, the developing of imaging techniques may greatly improve pain evaluation, although the inherent subjective component of pain may constitute an important limitation in the development of valid and reliable techniques.