It has been more than 25 years since Smythe and Moldofsky refocused attention on the fibromyalgia syndrome (FMS) (1). Their observations clearly characterized the predictable clinical features of this common pain syndrome and initiated new enquiry into an enigmatic disorder. The core characteristic of widespread pain was seen to occur in conjunction with the presence of widespread tenderness, implying complex changes to the neurophysiologic activities of the pain system. Smythe and Moldofsky emphasized the intimate link between the "physical" symptoms and signs of fibromyalgia, on the one hand, and the presence of a number of personal and emotional factors, on the other hand. Importantly, these investigators delineated abnormalities of sleep architecture, an early indication of the mind and body interactions in this disorder.As time has passed, research has identified significant biologic, psychological, and social abnormalities and effects in FMS. It has taken some time for this jigsaw of observations to form a coherent picture of the nature of FMS. As a consequence, it has also taken a long time to establish effective management strategies for this important clinical and societal problem.
Understanding FMS symptomsMany of the initial advances in the understanding of FMS have come from simple clinical observations. For instance, the generalized tenderness in FMS patients, more obvious in some sites than in others, has subsequently been shown to be due to the fundamental biologic process of sensitization as it pertains to the pain system (2,3). The stimulus threshold required to translate an otherwise innocuous sensory input, such as pressure, into pain is significantly lowered in FMS. This ubiquitous neurobiologic process is common to many different parts of the nervous system and translates otherwise subclinical information into perceived sensations, often resulting in unpleasant symptoms. Sensitization is an important function of the pain system after tissue damage, seen both peripherally and centrally, but it is also prominent in pain conditions without obvious tissue damage-induced pain generation, such as FMS. Consideration of this sensitization process in the dorsal horn of the spinal cord can be seen as a useful starting point in the understanding of FMS.Activity within both the unmyelinated C fibers, with related neuropeptide functions including those of substance P, and the faster-transmitting myelinated A-delta fibers is increased in FMS (4,5). These key nociceptor fiber types principally connect to nociceptivespecific projection neurons in the superficial layers of the dorsal horn (Figure 1). A minority of these fiber types also connect to the wide-dynamic range projection neurons, responsive to a broader range of input stimuli and usually more deeply placed in the dorsal horn.Perhaps even more important from the point of view of FMS is the input from the mechanoreceptors, the A-beta fiber system, that predominantly provides sensory proprioceptive information. Although most of this information is rel...