fMRI Identifies Brain Process Linking Pain Catastrophizing to Pain Widespreadness in Fibromyalgia
Key findings
- This study combined information from digital pain body maps and resting-state brain functional MRI data from 79 women with fibromyalgia to examine the association between pain widespreadness across the body, catastrophizing and brain network connectivity
- Pain catastrophizing was associated with increased pain widespreadness—fibromyalgia patients who reported more widespread pain across their body also reported greater catastrophizing thoughts about their pain, and vice versa
- Pain widespreadness was associated with increased connectivity between the brain's salience network (SLN) to the posterior cingulate cortex (PCC), a key node of the default mode network
- The strength of SLN–PCC connectivity mediated the association between pain widespreadness and catastrophizing
- Rather than having a direct role in nociception, the PCC likely has a higher-level role in chronic pain, underpinning cognitive processes such as self-referential cognition and catastrophizing about pain
Brain imaging studies using functional MRI (fMRI) have identified several differences (compared to matched healthy adults) in resting brain connectivity of the salience network (SLN) to nodes of the default mode network (DMN) in patients with chronic pain, including those with fibromyalgia.
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These differences may be facilitated by pain catastrophizing, a negative cascade of helplessness, pessimism, rumination and feelings of hopelessness about actual or anticipated pain. For example, researchers at Massachusetts General Hospital recently reported in Arthritis & Rheumatology that catastrophizing about fibromyalgia pain is associated with amplified activation in nodes of the DMN, which encode self-referential cognition and show altered functioning in chronic pain.
Building on this research, Vitaly Napadow, PhD, LAc, director of the Center for Integrative Pain NeuroImaging at the Martinos Center for Biomedical Imaging at Mass General, Dan-Mikael Ellingsen, PhD, at the time of the study a postdoctoral fellow at the Martinos Center, and colleagues have associated brain cross-network connectivity with both pain catastrophizing and pain widespreadness in patients with fibromyalgia. In fact, the connectivity strength was found to mediate the association between pain widespreadness and catastrophizing, suggesting that this altered connectivity pattern maintains the linkage between these clinical and behavioral aspects of fibromyalgia. The findings are detailed in Pain.
Study Methods
The researchers asked 79 women with fibromyalgia, 18–65 years old, to complete the Pain Catastrophizing Scale (PCS) and map their current pain on a body outline on a tablet computer. At each body location, participants indicated the type of pain sensation, tissue type and pain intensity.
Using conventional software, the researchers combined pixel-by-pixel analysis of the pain maps with multivoxel analysis of resting-state functional MRI data.
Pain Widespreadness
Regardless of sensation type (aching, burning, shooting or tenderness), participants reported relatively high pain widespreadness (the percent of the entire body marked as painful). The average was 27% but could also be reported as much higher, suggesting significant variability in the extent to which different body areas are affected by fibromyalgia. Interestingly, there was a significant positive correlation between pain widespreadness and pain catastrophizing.
Pain Catastrophizing
Pain catastrophizing (PCS total score) was positively correlated with pain intensity—regardless of sensation type—in the lower back, neck/upper back, shoulders/upper arms, thighs and legs. Regarding individual sensations, pain catastrophizing was:
- Positively correlated with aching pain in the lower back, neck and shoulders and with leg-related burning and shooting pain
- Negatively associated with burning and shooting pain in the back and the face and shooting pain in the back of the head
Pain Widespreadness and Network Connectivity
Pain widespreadness was positively associated with SLN connectivity to the:
- Posterior cingulate cortex (PCC), a key node of the DMN
- Dorsolateral prefrontal cortex, which is commonly activated in response to evoked pain and has an important role in endogenous downregulation of pain; its subregions constitute central nodes of the SLN, DMN and frontoparietal control (executive control/attention) network
- Left primary somatosensory cortex
- Anterior insula, a key hub of the SLN
Mediation of the Association Between Pain Catastrophizing and Widespreadness
There were significant direct linear associations between:
- Pain catastrophizing and pain widespreadness
- Pain catastrophizing and SLN–PCC connectivity
- SLN–PCC connectivity and pain widespreadness
Further statistical analysis suggested SLN–PCC connectivity is the mediating factor between pain catastrophizing and pain widespreadness regardless of overall pain intensity.
A Picture Is Worth a Thousand Words
Combining digital pain drawings with neuroimaging may be key to understanding fibromyalgia and other chronic pain conditions in which pain widespreadness, clustering, intensity and other parameters vary widely between patients.
This study suggests the PCC is a brain region that may not have a direct role in nociception but rather is involved in cognitive processes such as self-referential cognition and pain catastrophizing. A better understanding of how sensory and psychological processes interact during the development of chronic pain should ultimately aid the development of new therapeutic approaches.
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