Somatosensory evaluation in Dysfunctional Syndrome patients.

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.