Graph-theoretical analysis of resting-state fMRI in pediatric obsessive-compulsive disorder

•fMRI small-worldness is lower in OCD children suggesting inefficient neuronetworks.•Modularity is lower in OCD children suggesting alternative brain organization.•Local clustering coefficient is higher in OCD in severalbrain regions.•Local betweenness centrality is lower in OCD in the same regions.

BackgroundfMRI graph theory reveals resting-state brain networks, but has never been used in pediatric OCD.MethodsWhole-brain resting-state fMRI was acquired at 3 T from 21 children with OCD and 20 age-matched healthy controls. BOLD connectivity was analyzed yielding global and local graph-theory metrics across 100 child-based functional nodes. We also compared local metrics between groups in frontopolar, supplementary motor, and sensorimotor cortices, regions implicated in recent neuroimaging and/or brain stimulation treatment studies in OCD.ResultsAs in adults, the global metric small-worldness was significantly (P<0.05) lower in patients than controls, by 13.5% (%mean difference=100%X(OCD mean - control mean)/control mean). This suggests less efficient information transfer in patients. In addition, modularity was lower in OCD (15.1%, P<0.01), suggesting less granular - or differently organized - functional brain parcellation. Higher clustering coefficients (23.9-32.4%, P<0.05) were observed in patients in frontopolar, supplementary motor, sensorimotor, and cortices with lower betweenness centrality (−63.6%, P<0.01) at one frontopolar site. These findings are consistent with more locally intensive connectivity or less interaction with other brain regions at these sites.LimitationsRelatively large node size; relatively small sample size, comorbidities in some patients.ConclusionsPediatric OCD patients demonstrate aberrant global and local resting-state network connectivity topologies compared to healthy children. Local results accord with recent views of OCD as a disorder with sensorimotor component.