Fibromyalgia and reflex sympathetic dystrophy share defining characteristics, namely chronic pain and allodynia, as well as other important clinical features such as onset after trauma, female predominance, paresthesia, vasomotor instability, response to sympathetic blockade and anxiety/depression. Recent research using heart rate variability analysis demonstrated that patients with fibromyalgia have changes consistent with relentless circadian sympathetic hyperactivity. I propose that fibromyalgia is a sympathetically maintained pain syndrome in which ongoing sympathetic hyperactivity sensitizes the primary nociceptors and induces widespread pain and allodynia.

Clin Exp Rheumatol 2001; 19(1): 1-3