Objective. To use functional magnetic resonance imaging (fMRI) to evaluate the pattern of cerebral activation during the application of painful pressure and determine whether this pattern is augmented in patients with fibromyalgia (FM) compared with controls.Methods. Pressure was applied to the left thumbnail beds of 16 right-handed patients with FM and 16 right-handed matched controls. Each FM patient underwent fMRI while moderately painful pressure was being applied. The functional activation patterns in FM patients were compared with those in controls, who were tested under 2 conditions: the "stimulus pressure control" condition, during which they received an amount of pressure similar to that delivered to patients, and the "subjective pain control" condition, during which the intensity of stimulation was increased to deliver a subjective level of pain similar to that experienced by patients.Results. Stimulation with adequate pressure to cause similar pain in both groups resulted in 19 regions of increased regional cerebral blood flow in healthy controls and 12 significant regions in patients. Increased fMRI signal occurred in 7 regions common to both groups, and decreased signal was observed in 1 common region. In contrast, stimulation of controls with the same amount of pressure that caused pain in patients resulted in only 2 regions of increased signal, neither of which coincided with a region of activation in patients. Statistical comparison of the patient and control groups receiving similar stimulus pressures revealed 13 regions of greater activation in the patient group. In contrast, similar stimulus pressures produced only 1 region of greater activation in the control group.Conclusion. The fact that comparable subjectively painful conditions resulted in activation patterns that were similar in patients and controls, whereas similar pressures resulted in no common regions of activation and greater effects in patients, supports the hypothesis that FM is characterized by cortical or subcortical augmentation of pain processing.Fibromyalgia (FM) is characterized by chronic widespread pain (involving all 4 quadrants of the body as well as the axial skeleton) and diffuse tenderness (1). Population-based studies have demonstrated that FM affects ϳ2-4% of the population, with a very similar prevalence in at least 5 industrialized countries (2,3). The etiology of FM remains elusive, although there is support for the notion that altered central pain processing is a factor in the presentation of this disease. The development of functional brain imaging techniques provides an opportunity to examine central pain processing in patients with FM.Although the clinical diagnosis of FM is based on detecting 11 of 18 tender points (regions that are painful when manually palpated with 4 kg of pressure), increased sensitivity to pressure in this condition extends beyond tender points and involves the entire body (4-7). In aggregate, psychophysical studies demonstrate that patients with FM and control subjects generally dete...

Anatomical and physiological studies in animals, as well as functional imaging studies in humans have shown that multiple cortical areas are activated by painful stimuli. The view that pain is perceived only as a result of thalamic processing has, therefore, been abandoned, and has been replaced by the question of what functions can be assigned to individual cortical areas. The following cortical areas have been shown to be involved in the processing of painful stimuli: primary somatosensory cortex, secondary somatosensory cortex and its vicinity in the parietal operculum, insula, anterior cingulate cortex and prefrontal cortex. These areas probably process different aspects of pain in parallel. Previous psychophysical research has emphasized the importance of separating pain experience into sensory-discriminative and affective-motivational components. The sensory-discriminative component of pain can be considered a sensory modality similar to vision or olfaction; it becomes more and more evident that it is subserved by its own apparatus up to the cortical level. The affective-motivational component is close to what may be considered 'suffering from pain'; it is clearly related to aspects of emotion, arousal and the programming of behaviour. This dichotomy, however, has turned out to be too simple to explain the functional significance of nociceptive cortical networks. Recent progress in imaging technology has, therefore, provided a new impetus to study the multiple dimensions of pain.

Pain catastrophizing, or characterizations of pain as awful, horrible and unbearable, is increasingly being recognized as an important factor in the experience of pain. The purpose of this investigation was to examine the association between catastrophizing, as measured by the Coping Strategies Questionnaire Catastrophizing Subscale, and brain responses to blunt pressure assessed by functional MRI among 29 subjects with fibromyalgia. Since catastrophizing has been suggested to augment pain perception through enhanced attention to painful stimuli, and heightened emotional responses to pain, we hypothesized that catastrophizing would be positively associated with activation in structures believed to be involved in these aspects of pain processing. As catastrophizing is also strongly associated with depression, the influence of depressive symptomatology was statistically removed. Residual scores of catastrophizing controlling for depressive symptomatology were significantly associated with increased activity in the ipsilateral claustrum (r = 0.51, P < 0.05), cerebellum (r = 0.43, P < 0.05), dorsolateral prefrontal cortex (r = 0.47, P < 0.05), and parietal cortex (r = 0.41, P < 0.05), and in the contralateral dorsal anterior cingulate gyrus (ACC; r = 0.43, P < 0.05), dorsolateral prefrontal cortex (r = 0.41, P < 0.05), medial frontal cortex (r = 0.40, P < 0.05) and lentiform nuclei (r = 0.40, P < 0.05). Analysis of subjects classified as high or low catastrophizers, based on a median split of residual catastrophizing scores, showed that both groups displayed significant increases in ipsilateral secondary somatosensory cortex (SII), although the magnitude of activation was twice as large among high catastrophizers. Both groups also had significant activations in contralateral insula, SII, primary somatosensory cortex (SI), inferior parietal lobule and thalamus. High catastrophizers displayed unique activation in the contralateral anterior ACC, and the contralateral and ipsilateral lentiform. Both groups also displayed significant ipsilateral activation in SI, anterior and posterior cerebellum, posterior cingulate gyrus, and superior and inferior frontal gyrus. These findings suggest that pain catastrophizing, independent of the influence of depression, is significantly associated with increased activity in brain areas related to anticipation of pain (medial frontal cortex, cerebellum), attention to pain (dorsal ACC, dorsolateral prefrontal cortex), emotional aspects of pain (claustrum, closely connected to amygdala) and motor control. These results support the hypothesis that catastrophizing influences pain perception through altering attention and anticipation, and heightening emotional responses to pain. Activation associated with catastrophizing in motor areas of the brain may reflect expressive responses to pain that are associated with greater pain catastrophizing.

Objective. For many individuals with chronic low back pain (CLBP), there is no identifiable cause. In other idiopathic chronic pain conditions, sensory testing and functional magnetic resonance imaging (fMRI) have identified the occurrence of generalized increased pain sensitivity, hyperalgesia, and altered brain processing, suggesting central augmentation of pain processing in such conditions. We compared the results of both of these methods as applied to patients with idiopathic CLBP (n ‫؍‬ 11), patients with widespread pain (fibromyalgia; n ‫؍‬ 16), and healthy control subjects (n ‫؍‬ 11).Methods. Patients with CLBP had low back pain persisting for at least 12 months that was unexplained by MRI/radiographic changes. Experimental pain testing was performed at a neutral site (thumbnail) to assess the pressure-pain threshold in all subjects. For fMRI studies, stimuli of equal pressure (2 kg) and of equal subjective pain intensity (slightly intense pain) were applied to this same site.Results. Despite low numbers of tender points in the CLBP group, experimental pain testing revealed hyperalgesia in this group as well as in the fibromyalgia group; the pressure required to produce slightly intense pain was significantly higher in the controls (5.6 kg) than in the patients with CLBP (3.9 kg) (P ‫؍‬ 0.03) or the patients with fibromyalgia (3.5 kg) (P ‫؍‬ 0.006).When equal amounts of pressure were applied to the 3 groups, fMRI detected 5 common regions of neuronal activation in pain-related cortical areas in the CLBP and fibromyalgia groups (in the contralateral primary and secondary [S2] somatosensory cortices, inferior parietal lobule, cerebellum, and ipsilateral S2). This same stimulus resulted in only a single activation in controls (in the contralateral S2 somatosensory cortex). When subjects in the 3 groups received stimuli that evoked subjectively equal pain, fMRI revealed common neuronal activations in all 3 groups.Conclusion. At equal levels of pressure, patients with CLBP or fibromyalgia experienced significantly more pain and showed more extensive, common patterns of neuronal activation in pain-related cortical areas. When stimuli that elicited equally painful responses were applied (requiring significantly lower pressure in both patient groups as compared with the control group), neuronal activations were similar among the 3 groups. These findings are consistent with the occurrence of augmented central pain processing in patients with idiopathic CLBP.Chronic low back pain (CLBP) is one of the most common and expensive musculoskeletal disorders in developed countries (1,2). Back pain in general affects 70-85% of all people at some time in their lives, but 90% of affected individuals recover, typically within 12 weeks (3). Recovery after 12 weeks is slow and uncertain, and this subset of patients with CLBP accounts for major expenses in the health care and disability systems (2,4).Despite the magnitude of the problem, little is known about the precise cause of CLBP. There is often a mismatch between objectiv...