Neurobiologic Features of Fibromyalgia Are Also Present Among Rheumatoid Arthritis Patients

Objectives: Many rheumatoid arthritis (RA) patients report pain despite excellent control of inflammation with immunotherapies. Variable degrees of co-existing fibromyalgia (FM) may explain this disparity. FM has been characterised by aberrant brain functional connectivity, especially between the Default Mode Network (DMN) and insula. We hypothesised that RA patients reporting the highest 2011 ACR FM survey criteria scores- a continuous measure of FM degree also known as fibromyalgianess (FMness)- would demonstrate functional connectivity abnormalities similar to FM. Methods: RA patients underwent an 11 min functional connectivity MRI brain scan (fcMRI) and a clinical evaluation which included a measure of FMness. Brain networks were isolated from FcMRI data. Individual patient network to whole brain connectivity analyses were then conducted followed by group level regression which correlated the connectivity of each network with FMness. Results were significant on the cluster level with a family wise error (FWE) rate p-value <0.05 derived from an uncorrected voxel level p-value <0.001. Results: 54 patients participated (mean age 54.9years; 75.9% female; mean FMness score 13.3 [range 1-29]). From the whole brain analyses, a single significant positive correlation between DMN connectivity to the left mid/posterior insula and FMness (r=0.58, p=0.001 FWE) was demonstrated. Conclusions: RA patients who have increased levels of FMness appear to share neurobiological features consistently observed in FM patients. This study is the first to provide neuroimaging evidence that RA is a mixed pain state, with many patients’ symptoms being related to CNS rather than classic inflammatory mechanisms.