Fibromyalgia and Related Medically Unexplained Symptoms: A Lost Link Between Cardiovascular and Nociception Modulation

Abstract

Objectives: Fibromyalgia syndrome [FMS] is one of the most common causes of widespread pain and fatigue, associated with significant morbidity. It is characterized by chronic widespread body pain and a defined number of tender points, as well as multisystem-related alterations. There is considerable diagnostic overlap with chronic fatigue syndrome. Mainstay theory states that these findings could be caused by a central sensitization phenomenon that would lead to diffused hyperalgesia. Until now, however, little is known about the nature of this central sensitization and the possible causative events that lead to it. We sought to review the current evidence about FMS, its relation to cardiovascular alterations [dysautonomia], and to propose a new model upon its physiopathogenesis.

Findings: Fibromyalgia syndrome patients have a greater incidence of orthostatic intolerance, characterized by pre-syncope symptoms and a relentless activated sympathetic system, perhaps causally related to FMS. Independent authors have theorized that orthostatic intolerance has a causal link to FMS. Recently it has been demonstrated that alterations in small vessel tone and endothelial function of skeletal muscle or splanchnic vascular beds are crucial to the development of orthostatic intolerance.

Conclusions: We propose two novel hypotheses: FMS would be related to a derangement in cardiovascular autonomic control secondary to endothelial function disturbance and this cardiovascular derangement could correlate with attenuation of supraspinal descending nociceptive inhibition through an integrated central nervous system modulation.

KEYWORDS:

• Fibromyalgia syndrome
• hyperalgesia
• central sensitization
• orthostatic intolerance
• endothelial dysfunction
• pain modulation