RSI revisited: evidence for psychological and physiological differences from an age, sex and occupation matched...

The present study sought to examine psychological characteristics and function of primary afferent nociceptive mechanisms, as indexed by capsaicin-induced flare responses, in subjects suffering from RSI (n = 72) and in pain free control volunteers (n = 69). After completing a battery of psychological tests including the McGill Pain Questionnaire, Visual Analogue Scale and Word Descriptor Scale for pain, the Profile of Mood States, Illness Behaviour Questionnaire and Multidimensional Health Locus of Control, the neurogenic flare response was assessed on the right and left forearms and across the trapezius at the shoulder. When compared to controls RSI subjects displayed higher levels of mood disturbance and some abnormal patterns of illness behaviour. A reduction in flare size was observed in the pain affected limb of RSI subjects, but an increased response occurred in sites reported as unaffected by clinical pain. Multiple regression analysis revealed that the severity of clinical pain was strongly associated with the magnitude of reduction in flare size. Collectively, these findings provide objective evidence of altered nociceptor mechanisms in RSI subjects, and are consistent with the view that this chronic pain syndrome involves somatic pathophysiology. However, a strong conviction regarding the somatic basis of their symptoms, and a denial of psychological factors may have contributed to the more severe affective disturbance and greater subjective emphasis on the presence of pain.