There appears to be as yet undefined but significant and possibly multifactorial elements of personality, stress, or depression in the manifestations and possibly the pathogenesis of FS. If these factors, perhaps amplified by the neurophysiologic effects of disturbed sleep, produce a neurochemical disturbance in CNS function, and if this perturbation includes a reduction or impairment of function involving the pain-modulation pathways, then a simple and perhaps compelling explanation for the experience of pain in FS becomes apparent. Reduced midbrain/brainstem inhibition of ascending nociceptive impulses would clearly explain the finding of tender points in normal-appearing areas of the body, as well as the lack of segmental distribution of discomfort in FS. Local anesthetics, injected peripherally into tender points, would be expected, as is the case, to block pain and tenderness in the local area for the duration of action of the agent used. Analgesics with peripheral activity, such as aspirin and NSAIDs, are relatively ineffective in treating FS, and would be predictably so in a disorder involving reduced central pain inhibition as opposed to increased peripheral nociceptive input. It would not be surprising to find that centrally acting agents, particularly those producing enhancement of serotonergic neurons such as amitriptyline, would provide substantial or total pain relief as well as improvement in mood in a significant number of patients. Most importantly, this concept would highlight the real pain experienced by these patients and the obligation of involved physicians to appropriately diagnose and treat this common pain syndrome. Avoiding excessive conjecture, it is then permissible at the present time to conclude that: FS is a characteristic, clinically common pain syndrome in which aspects of the pain itself appear to be of physiologic origin. Although stress or inherent personality traits may play a role in FS, the relative uniformity in symptomatology virtually excludes conversion hysteria as a major factor in this disorder. The lack of evidence for a disturbance in muscle, fascia, and other soft tissues in FS, the lack of adequate response to NSAIDs, and the frequent response to TCAs suggest that specific dysfunction of the CNS may play a major role in the symptomatology of this entity. Impaired function of the pain-modulation system, located anatomically in the midbrain and brainstem, provides a plausible explanation for the pain and finding of tender points in FS, as well as a potentially rational basis for therapy.
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