Fibromyalgia and Soft Tissue Disorders II-Central Nervous System

A handful of abstracts were presented during this session, focusing on the link between fibromyalgia fatigue and kynurenine pathway activity, glutamate in the anterior insula, the effects of fatigue on response to pain, and neurocortical representation of locus of control in patients with fibromyalgia.

Kynurenine Pathway Activity Linked to Fibromyalgia FatiguePresentation Number: 1991

Researchers: Boomershine C, Titova d, Zhu C, et al.

Purpose: The test the hypothesis that increased kynurening pathway (KYN-p) activity causes fibromyalgia (FM) fatigue-which the authors say is often the most disabling FM symptom-by studying KYN-p activity and fatigue levels in patients with FM and a mouse FM model.

Results: Boomershine and colleagues concluded that increased "KYN-p activity is associated with FM fatigue in humans and a murine model" and that indoleamine 2,3-dioxygenase (the rate-limiting KYN-p enzyme) "inhibition may be a novel method for treating FM fatigue."

Glutamate in the Anterior Insula Is Associated with Working Memory Performance in Fibromyalgia (FM)Presentation Number: 1993

Researchers: Barjola P, Glass J, Sundgren P, et al.

Purpose: To test the hypothesis that anterior insular glutamate (Glu) may be related to working memory (WM) performance, as the concentration of Glu "within the posterior insula has been shown to be related to pain processing in fibromyalgia (FM)," the role played by Glu "in the anterior insula in FM is less understood," "FM is also associated with multiple cognitive impairments such as reduced" WM, and "insular structures have been previously shown to be involved in different aspects of memory function."

Results: "Consistent with previous literature, the anterior and posterior regions of the insula appear to be functionally distinct. This study suggests that anterior insula Glu may be involved in WM whereas previous studies suggest that the posterior insula is involved in pain processing. Future studies are needed to understand the mechanisms underlying these relationships which may be relevant to other chronic pain populations."

Bilateral Anterior Insular Glutamate (Glu) Is Asymmetrically Associated with Experimental Pain in Individuals with Fibromyalgia and Pain-free ControlsPresentation Number: 1994

Researchers: Harris R, Sundgren P, Hubbard J, et al.

Purpose: To examine "the relative levels of glutamate (Glu), an excitatory neurotransmitter, within the right and left anterior insula of individuals with fibromyalgia (FM) and pain-free controls (HC)" using proton magnetic resonance spectroscopy (H-MRS), in order to test the hypothesis "that greater levels of Glu in the right anterior insula as compared to the left, would be associated with more pain sensitivity," as it "has been suggested that there is an asymmetric distribution in function within [the insula], with the right anterior insula being responsive to pain stimuli and the left playing more of a pain inhibiting role."

Results: In the anterior insulae, an asymmetric distribution of Glu function appears to exist, with more pain sensitivity associated with greater "excitatory neural activity in the right anterior insula, as compared to the left," a relationship that Harris and colleagues feel may "represent a general aspect of pain processing."

Fatigue Enhances the Response to Pain through NMDA Receptors in Nucleus Raphe ObscurusPresentation Number: 1995

Researchers: daSilva L, Rasmussen L, Sluka K

Purpose: To test "if fatigue would enhance the response to pain in male and female mice; and if this fatigue-enhancement of pain behaviors was centrally mediated" using "a mouse-model of fatigue combined with a mouse-model of chronic widespread pain to examine the interactions between pain and fatigue," as "many people with chronic fatigue present with pain and many people with chronic pain present with fatigue."

Results: The authors found that, through central mechanisms that involve NMDA receptors in the nucleus raphe obscurus, pain is enhanced by fatigue.

Neurocortical Representation of Locus of Control in Individuals with FibromyalgiaPresentation Number: 1996

Researchers: Williams D, Harris R, Bhavsar R

Purpose: To "identify neurocortical regions experiencing greater changes in activity as I-loc increases in individuals with FM exposed to evoked pain stimuli," with the understanding that cognitive "modulation of pain is thought to involve dorsolateral, ventrolateral, and medial prefrontal cortical regions (PFC)-regions that have been associated with placebo responsively, expectations for pain relief, and perceived control over pain"-and the "perception of pain control associated with PFC activity is thought to initiate downstream modulation of the pain matrix and ultimately brain-stem mediated analgesic responses."

Results: The researchers' hypothesis was supported by their finding that "perceived control over pain is associated with PFC activation and with semantic regions related to but differentiated from the pain matrix." They added that non-pharmacologic "interventions appear to modify perceptions of pain control which in turn influence neurocortical regions important to pain perception and modulation."