Dados do Trabalho

Título

THE MEDIATION OF RESTING-STATE FUNCTIONAL CONNECTIVITY BY THE SEVERITY OF SYMPTOMS IN FIBROMYALGIA DEPENDS ON THE DYSFUNCTION OF THE DESCENDING PAIN MODULATORY SYSTEM

Introdução

Fibromyalgia (FM) is a chronic pain syndrome characterized by widespread pain and increased levels of emotional distress, sleep disorders, and cognitive abnormalities. The dysfunction of the Descending Pain Modulatory System (DPMS) is a pathophysiological feature of FM, with already shown decreased resting state functional connectivity (rsFC) between pain processing cortical areas with this set of neural networks. The conditioned pain modulatory test (CPM-test) is a paradigm for assessing the DPMS function through the measurement of nervous adaptability to attenuate pain signalling in response to prior pain stimulation, in which non response implies a DPMS dysfunction.

Objetivo

To test if the clinical symptom of FM mediates the rsFC between pain processing cortical areas and the periaqueductal gray matter in the midbrain (PAG) in responder and non-responder patients to the CPM-test.

Método

Transversal study that included 33 female subjects, aged 30–60 years old, right-handed, literate FM patients according to the American College of Rheumatology (ACR) criteria (2016). CMP-test was performed immersing subjects’ non-dominant hand in cold water (zero to 1°C degree), that classified them either as non-responders (n=13) or responders (n=20). rsFMRI was recorded over 10 minutes of rsFC using a 3T scanner. Data was processed in the toolbox CONN18 using SPM12 commands in MATLAB®. Pain intensity was assessed by the ACR 2016 criteria, central sensitization by the Central Sensitization Inventory, disability due to pain by the Disability by Profile of Chronic Pain: Screen, and catastrophizing thinking by the Pain Catastrophizing Scale. We accepted a type I error of 5% and all analyses were adjusted for multiple comparisons by the Bonferroni test. Statistical analyses were performed using SPSS22.0.

Resultados

Non-responders had lower rsFC between the left primary somatosensory cortex (S1) and the PAG (t = 4.96, p ≤0.001). Generalized linear model revealed a main effect according to responders and non-responders to CPM-test on the S1-PAG rsFC (χ²=5.35, DF=1, p< 0.02). The S1-PAG rsFC is mediated by the severity of pain intensity (p=0.04), disability levels (p<0.01), central sensitization symptoms (p=0.02), and pain catastrophizing (p<0.01).

Conclusão

The reduced S1-PAG rsFC may be a biomarker of DPMS dysfunction and disability due to pain in FM, with potential translational use in follow-up and in predicting response to treatment.

Palavras-chave

Fibromyalgia, functional connectivity, pain processing