P28. Sympathetic activity in patients with fibromyalgia – A microneurographic study

Abstract

Introduction Fibromyalgia is a disease which is characterized by -“widespread pain”-, one aspect of the pathophysiology might be a central dysregulation of autonomic as well as endocrine parameters. The baroreflexsensitivity (BRS) is being discussed as a connecting link. The nucleus tractus solitarii (NTS) was identified as a crucial structure of the BRS which is important for the regulation of sympathetic functions such as blood pressure and heart frequency but also for the central regulation of pain perception. The physiological state of an inverse relation between blood pressure and pain perception is diminished in patients with fibromyalgia. An efferent arm of the baroreflex is the vasoconstrictor activity of the muscle vessels (MSNA; muscle-sympathetic-nerve-activity) which can be directly assessed by the method of microneurography. The aim of this study was to detect differences of sympathetic activity between fibromyalgia patient and healthy controls by directly measuring the sympathetic outflow using the method of microneurography. Methods MSNA was obtained from 12 patients with fibromyalgia and 11 healthy controls. MSNA was recorded from the peroneal nerve during rest (baseline) and during baroreflex-stimulation by lower-body-negative-pressure (LBNP, −40 mmHg). Analyzed were burst frequency (burst per minute) and burst incidence (burst per hundred heart beats) as well as the autonomic parameters as blood pressure, heart rate variability and baroreflexsensitivity. Results The microneurographic data shows that the burst frequency of fibromyalgia patients is a higher in the baseline ( T = 2.675, p = 0.014) and during LBNP ( F = 5.571, p = 0.03) compared to the healthy controls, the same tendency was visible for burst incidence but level of significance was not reached. The relative increase in BF and BI by LBNP did not differ between the FM-patients and controls. The other autonomic parameters showed a decreased baroreflexsensitivity and increased blood pressure in FM patients compared to controls. Analysis of heart rate variability revealed decresed vagal activity in FM patients. Conclusion So far our results show an autonomic dysbalance with a higher sympathetic activity in the FM-patients compared to the healthy volunteers. The higher outflow of sympathetic activity may play a vital role in the pathophysiological mechanisms of developing fibromyalgia.