Somatosensory evaluation in Dysfunctional Syndrome patients.

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Many chronic pain patients are refractory to treatment, which leads to the suspicion that somehow they are not fully effective and probably some mechanism of pain generation and/or maintenance is still unknown. The aim of this cross-sectional study was to provide evidence-based data on pain mechanisms in different types of chronic pain conditions. Eighty women, with 18-65 years old, were included, divided into four groups: myofascial pain of the masticatory muscles (n = 20), fibromyalgia (n = 20), chronic daily headache and healthy volunteers (n = 20). All patients were submitted to quantitative sensory tests: pressure pain threshold, mechanical detection threshold, mechanical pain threshold, ischaemic pain tolerance, cold pain sensitivity, aftersensation, wind-up ratio and conditioned pain modulation. Current perception threshold was also determined (Neurometer CPT/C - Neurotron). Three different zones were evaluated: trigeminal (masseter muscle), cervical and extratrigeminal (thenar eminence). Data were recorded and subjected to statistical analysis (anova, Tukey and Student's t-tests). Masticatory myofascial pain, fibromyalgia and chronic daily headache individuals presented lower pressure pain thresholds than healthy volunteers (P = 0.00). Chronic daily headache individuals had a significantly higher mechanical detection threshold than healthy volunteers (P = 0.01). Individuals of the symptomatic groups showed lower values for mechanical pain threshold and for ischaemic pain tolerance (P = 0.00) than healthy volunteers. The ability to activate the mechanism of endogenous modulation is impaired in women with fibromyalgia and myofascial pain (P = 0.00). These results reinforce evidence of central sensitisation and impaired endogenous modulation system in individuals with myofascial pain, fibromyalgia and chronic daily headache.