Association between altered baroreflex control and pain intensity in fibromyalgia.

BACKGROUND: The role of the sympathetic nervous system dysfunction in fibromyalgia (FM) is unclear. A large series of studies has shown that various abnormalities of the autonomic nervous system are present in fibromyalgia and contribute at least in part to the patients’ complaints and symptoms. METHODS: In FM patients (n = 10) and healthy controls (HC; n = 11) pain intensity (numeric rating scale; NRS), cardiac baroreflex sensitivity (BRS) and muscle sympathetic nerve activity (MSNA) via microneurography at rest and during baroreflex stimulation (lower body negative pressure; LBNP) were assessed. RESULTS: Resting sympathetic activity was higher in FM at baseline (FM patients: 31.1 ± 2.3 bursts/min; HC: 24.3 ± 1.5 bursts/ min, F = 5.736; p = 0.028) and during baroreflex stimulation (F = 5.057; p = 0.044). Pain intensity correlated with MSNA activity (r = 0.760; p = 0.018) and showed a tendency to a negative correlation with BRS (r=-0.641; p = 0.063). CONCLUSION: Changes in the baroreflex circuit with increased sympathetic outflow are associated with increased pain perception in FM.