The role of autonomic system in Fibromyalgia

The researches of the last years have shown that patients with fibromyalgia have often dysfunction of the stress response system and is emerging that could be important in the pathogenesis of the syndrome.

The Autonomic nervous system(ANS) maintains all the involuntary functions such as  heart rate, digestion, respiratory rate, pupillary response, urination, sexual arousal etc.

This system is involved in the fight or flight reaction, therefore is involved every time that in presence of physical or emotional trauma.

This system has 2 branches – the parasympathetic and the sympathetic one. They have antagonist functions and there must be a balance between them to preserve the homeostasis.

Fibromyalgia seems to be related with ANS dysfunction. Previous studies have examined the “stellate ganglion block”*. The block of this collection of nerves shown an improvement in the regional pain and tenderness compared with the sham protocol.

Other studies have evaluated the autonomic nervous system activity, using different parameters, such as the production of norepinephrine, heart variability, muscle sympathetic activity and the use  tilt table test. All of them reached the same conclusion of  the presence of a dysfunction in the ANS.

Apparently a ceiling-effect seems to occur where due to an over-activity of the sympathetic system,  it becomes unable to respond to any further stressor, causing constant fatigue and morning stiffness.

Also, relentless sympathetic hyperactivity may explain symptoms such as sleep disorders, anxiety, pseudo-Raynaud’s phenomenon, intestinal irritability, Dryness of the exocrine glands(eyes, mouth) etc.

Around the pathogenesis of Fibromyalgia there are still a lot of question marks, but the study of autonomic nervous system may deserve a particular attention.

*The Stellate ganglion is collection of nerves (sympathetic) found at the level of the sixth and seventh cervical vertebrae of the neck. The block is done through an injection of medication into these nerves.

References:

Martinez-Lavin M(2007),Biology and therapy of fibromyalgia. Stress, the stress response system, and fibromyalgia.

doi: 10.1186/ar2146