Brain Structural Changes And Altered Pain Perception In Chronic Non-specific Low Back Pain With Depression

Background: Chronic non-specific low back pain(CNLBP)is a common musculoskeletal disease characterized by pain and dysfunction,which can be accompanied by non-pain symptoms such as depression,anxiety,and cognitive impairment.Studies have shown depression can aggravate pain presentations in chronic non-specific back pain(CNLBP)participants and seems associated with abnormal central pain processing.Although previous neuroimaging studies showed brain microstructure abnormality in CNLBP,most of them failed to take into account the condition of CNLBP with a comorbidity of depression.Little is known about the mediating effect of negative emotion as depression on the central response patterns of CNLBP.Purpose: This functional magnetic resonance imaging(MRI)study aimed to investigate the effect of depression on the CNLBP by evaluating the neurostructural measures and clinical pain and behavioral parameters,and to explore potential central mechanisms between CNLBP and depression.Methods: Totally 45 participants were included in the study,with 11 CNLBP patients with depression(CPD group),15 CNLBP non-depression(CP group),and 19 healthy controls(HC group).Voxel-based morphometry analysis(VBM)was performed to assess GMV differences among groups and their association with the clinical feature was examined by partial correlation analysis.The mediating effect of depression in the interaction between pain intensity and GMV was analyzed.The visual analgesia score(VAS),Oswestry disability index(ODI),Mc Gill pain questionnaire(SF-MPQ),the short form-36 health survey(SF-36),Beck anxiety inventory(BAI),Beck depression inventory-II(BDI)and pain catastrophizing scale(PCS)were employed.One-way analysis of variance and independent-sample t-test were used to analyze between-group differences for continuous data and nonparametric tests as the Kruskal Wallis test and Mann Whitney U test were adopted for categorical data.Results:(1)Compared with the HC group,CNLBP subjects showed significantly higher levels of dysfunction,pain catastrophizing scoring,anxiety,and depression,and lower quality of life.All these clinical parameters in the subgroup with depression(CPD)was more significant than the CP.(2)The volumes of right hippocampus/parahippocampal gyrus(R-HPC/PHA)and right superior temporal gyrus(R-STG)in CP group were large than that of both CPD group and HC group,with CPD group as the one with the least volumes.(3)Among CNLBP participants,VBM revealed a positive correlation between the VAS and regional GMV in the left superior temporal gyrus(L-STG)and the right parietal superior lobe(R-SPL),(P<0.001).Higher GMV in the left inferior parietal lobes(L-IPL)and lower GMV of right fusiform gyrus were correlated with higher PCS scores(P<0.001).Lower GMV of right caudate was associated with higher depression scores(P<0.001).(4)A significant mediation effect of depression was found in the association between GMV and pain intensity.Conclusion: In CNLBP,increased levels of depression may be associated with decreased volumes of hippocampus/para-hippocampal gyrus.Depression has a significant negative mediation effect between pain intensity and brain structure in CNBLP.