Disturbed insular functional connectivity and its clinical implication in patients with complex regional pain syndrome

Functional connectivity in complex regional pain syndrome: A bicentric study

Brain imaging studies in complex regional pain syndrome (CRPS) have found mixed evidence for functional and structural changes in CRPS. In this cross-sectional study, we evaluated two patient cohorts from different centers and examined functional connectivity (rsFC) in 51 CRPS patients and 50 matched controls. rsFC was compared in predefined ROI pairs, but also in non-hypothesis driven analyses. Resting state (rs)fMRI changes in default mode network (DMN) and the degree rank order disruption index (kD) were additionally evaluated. Finally, imaging parameters were correlated with clinical severity and somatosensory function. Among predefined pairs, we found only weakly to moderately lower functional connectivity between the right nucleus accumbens and bilateral ventromedial prefrontal cortex in the infra-slow oscillations (ISO) band. The unconstrained ROI-to-ROI analysis revealed lower rsFC between the periaqueductal gray matter (PAG) and left anterior insula, and higher rsFC between the right sensorimotor thalamus and nucleus accumbens. In the correlation analysis, pain was positively associated with insulo-prefrontal rsFC, whereas sensorimotor thalamo-cortical rsFC was positively associated with tactile spatial resolution of the affected side. In contrast to previous reports, we found no group differences for kD or rsFC in the DMN, but detected overall lower data quality in patients. In summary, while some of the previous results were not replicated despite the larger sample size, novel findings from two independent cohorts point to potential down-regulated antinociceptive modulation by the PAG and increased connectivity within the reward system as pathophysiological mechanisms in CRPS. However, in light of the detected systematic differences in data quality between patients and healthy subjects, validity of rsFC abnormalities in CRPS should be carefully scrutinized in future replication studies.

A Case of a Father and Son With Complex Regional Pain Syndrome Type 1 Exhibiting Different Resting-State Functional Connectivity on Functional MRI

Complex regional pain syndrome (CRPS) type 1 is a chronic pain condition whose pathogenesis involves changes in the central and peripheral nervous systems, with potential genetic contributions. Functional magnetic resonance imaging (fMRI) studies report that alterations in resting-state functional connectivity (rsFC) may reflect central nervous system anomalies in CRPS type 1. Herein, we describe the case of a father and son with CRPS type 1 who exhibited different rsFC patterns in fMRI analyses correlating with their individual CRPS phenotypes. A 39-year-old male and his 61-year-old father presented with severe pain and mobility limitations in their right upper limbs following a vehicle accident and a fall, respectively, and were diagnosed with CRPS type 1. Despite receiving treatment, they experienced severe pain and limited mobility. The son exhibited dystonia and musculoskeletal atrophy while the father experienced extensive sensory disturbances. Bone scintigraphy revealed increased uptake in affected regions. The patients' resting-state fMRI data were compared with those of 48 healthy adults using the CONN software, with the false discovery rate set at p<0.05. Distinct brain regions for the father and son exhibited decreased rsFC (between the rostral prefrontal cortex and orbitofrontal cortex in the father and between the supplementary motor area and pallidum in the son; all in the right hemisphere). These changes corresponded to pain sensation and cognitive-emotional alterations in the father and limb movement disorders (dystonia) in the son. Our findings strongly support the idea that abnormalities in rsFC are closely linked to CRPS type 1 phenotypes.