Diagnosis of Altered Central Pain Processing

Study Design. Nonsystematic review. Objective. To review the current knowledge on detecting altered central pain processing in individual patients with chronic pain. Summary of Background Data. Alterations in central pain processing are mainly characterized by hyperexcitability of the central nervous system and disturbances in endogenous pain modulation. Although these mechanisms are widely recognized as important determinants of pain and disability, there is need for translation of this knowledge into benefits for patients. To this purpose, the first step is the detection of abnormalities in pain processing in individual patients. Quantitative sensory tests (QST) explore aspects of nociception and pain perception, and are therefore potentially useful for diagnostic purposes. Methods. Nonsystematic review of the reliability, validity and reference values of QST for the assessment of altered central pain processing in chronic pain patients. Results. The reliability of QST is generally high. However, most studies have been performed on healthy volunteers, and few reliability data in patients are available. Furthermore, little is known on the reliability of measures of endogenous pain modulation. The face validity of QST is acceptable. The construct validity cannot be tested, because there is no gold standard for the detection of altered central pain processing in humans. Reference values of different types of QST for applications in neuropathic and musculoskeletal pain have been determined in large samples of pain-free subjects. Conclusion. QST can be used in clinical practice to assess the presence of sensory abnormalities in individual patients. Because information on the reliability and validity of the tests is incomplete, the findings should be interpreted with caution. It is still unclear to what extent disturbances in central pain processing are relevant for the determination of symptoms in individual patients. Furthermore, the therapeutic consequences of these assessments remain undetermined. These are challenges of future translational research.