Fibromyalgia: the nerve of that disease.

Fibromyalgia syndrome (FM) is a common, often debilitating and intractable, chronic, generalized pain condition. The development of effective therapies to treat FM has been hindered by a lack of understanding of fundamental mechanisms in the etiology of FM. In view of prominent characteristics that FM shares with other generalized pain conditions, we suggest that a key mechanism in such disorders may be that of altered activity in the subdiaphragmatic vagus nerve. Specifically, we propose that activity in vagal afferents, arising from the gastrointestinal tract, and sympathoadrenal function mediate a contribution of stress to FM and its strong association with irritable bowel syndrome. An important prediction of the proposed mechanism is that interventions that selectively modulate activity in specific populations of subdiaphragmatic afferents might be used to treat the symptoms of FM and other generalized pain syndromes.