Sensory dysfunction in fibromyalgia patients with implications for pathogenic mechanisms

Abstract

This study, addressing etiologic and pathogenic aspects of fibromyalgia (FM), aimed at examining whether sensory abnormalities in FM patients are generalized or confined to areas with spontaneous pain. Ten female FM patients and 10 healthy, age-matched females participated. The patients were asked to rate the intensity of ongoing pain using a visual analogue scale (VAS) at the site of maximal pain, the homologous contralateral site and two homologous sites with no or minimal pain. Quantitative sensory testing was performed for assessment of perception thresholds in these four sites. Von Frey filaments were used to test low-threshold mechanoreceptive function. Pressure pain sensitivity was assessed with a pressure algometer and thermal sensitivity with a Thermotest. In addition the stimulus-response curve of pain intensity as a function of graded nociceptive heat stimulation was studied at the site of maximal pain and at the homologous contralateral site. FM patients had increased sensitivity to non-painful warmth (P < 0.01) over painful sites and a tendency to increased sensitivity to non-painful cold (P < 0.06) at all sites compared to controls, but there was no difference between groups regarding tactile perception thresholds. Compared to controls, patients demonstrated increased sensitivity to pressure pain (P < 0.001), cold pain (P < 0.001) and heat pain (P < 0.02) over all tested sites. The stimulus-response curve was parallely shifted to the left of the curve obtained from controls (P < 0.003). Intragroup comparisons showed that patients had increased sensitivity to pressure pain (P < 0.01) and light touch (P < 0.05) in the site of maximal pain compared to the homologous contralateral site. These findings could be explained in terms of sensitization of primary afferent pathways or as a dysfunction of endogenous systems modulating afferent activity. However, the generalized increase in sensitivity found in FM patients was unrelated to spontaneous pain and thus most likely due to a central nervous system (CNS) dysfunction. The additional hyperphenomena related to spontaneous pain are probably dependent on disinhibition/facilitation of nociceptive afferent input from normal (or ischemic) muscles.

Generalized hypervigilance in fibromyalgia: Normal interoceptive accuracy, but reduced self-regulatory capacity

“…Although the small CI indicates robustness of the finding that the accuracy of detecting heart beats does not differ between FM patients and healthy controls, it is opposed to previous results showing increased pain sensitivity and amplified perception of painful and non-painful stimuli in FM patients (2,3,(7)(8)(9). The present finding, however, is in line with a number of studies, which failed to demonstrate prioritization of external innocuous stimuli in FM patients (4,41).…”

“…interoception, is scarce. So far, generalized hypervigilance has been supported by (a) self-report measures, on which FM patients typically show elevated scores for vigilance to pain (4)(5)(6) and (b) experimental measures showing decreased pain thresholds and tolerance levels for experimentally induced pain (2,7,8) innocuous (e.g. auditory) stimuli (3,9) and (c) perceptual amplification of nonaversive interoceptive stimulation (10) in FM patients.…”

Fibromyalgia patients and controls are equally accurate in detecting tactile stimuli while observing another in pain: an experimental study

“…The results are also not in line with those of Brown et al (2010), who suggested that there might be an interrelation between illusory tactile perceptions and the degree of pseudoneurological symptoms, nor with Katzer et al (2011) who suggested medically unexplained symptoms might be related to touch illusions, because both groups in the present study reported a comparable number of vicarious somatosensory experiences. Some previous studies have demonstrated that patients with FM have a hypersensitivity for mechanical, cold and heat pain perception (Kosek et al, 1996;Smith et al, 2008) and mixed results exist for non-painful sensations such as cold, warm and touch (Desmeules et al, 2003;Klauenberg et al, 2008). The results of the present study show that threshold intensities for vibrotactile stimuli, although individually determined, were not significantly different for both groups.…”

Treatment of cervical myelopathy in patients with the fibromyalgia syndrome: outcomes and implications

“…There are research findings suggesting that fibromyalgia may be a neurological disorder characterized by ''central sensitization''. Abnormalities in pain processing [5,23], central pain modulation [25,28] and secondary hyperalgesia [2] have been reported. There are also reports of reduced thalamic blood flow [24,30], and elevated levels of nerve growth factor [15] and the neurotransmitter substance P [36,42] in the cerebrospinal fluid of fibromyalgia patients.…”