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Parietal cortex differences identified among adults, children with OCD

Findings recently published in The American Journal of Psychiatry demonstrate that the parietal cortex is implicated in both adult and pediatric patients with OCD, with widespread cortical thickness abnormalities found in medicated adults and more pronounced surface area deficits found in children.

“An important limitation of brain imaging research is the typically small samples that limit sensitivity and presumably contribute to the lack of reproducibility and reliability of findings. This issue may be partially addressed by the use of meta- and mega-analysis of multiple study samples,” Premika S.W. Boedhoe, MSc, from the departments of psychiatry, and anatomy and neurosciences at VU University Medical Center in Amsterdam, and colleagues wrote. “Findings regarding the orbitofrontal cortex and the operculum have been inconsistent. These inconsistencies may be partially explained by differences in processing protocols, limited statistical power, and clinical heterogeneity related to variation in disease profile and developmental stage.”

Prior research has suggested involvement of fronto-limbic and fronto-parietal regions in pediatric and adult OCD. In this study, researchers conducted meta- and mega-analyses comprising a large study of cortical morphometry in OCD to determine the effect sizes for differences between pediatric and adult patients and controls, and associations with clinical characteristics. They processed T1-weighted MRI scans of 1,905 patients with OCD and 1,760 healthy controls from 27 sites worldwide using FreeSurfer to examine cortical thickness and surface area.

Analysis showed that for adult OCD patients compared with controls, there was a significantly lower surface area for the transverse temporal cortex and a thinner inferior parietal cortex. In addition, medicated adult patients showed thinner cortices throughout the brain. For pediatric OCD patients, there were significantly thinner inferior and superior parietal cortices compared with controls; however, none of the regions analyzed demonstrated significant differences in surface area for pediatric patients vs. controls. Medicated pediatric patients had lower surface area in frontal regions.

“These results support the hypothesis that the pathophysiology of OCD cannot be explained solely by alterations of the classical cortico-striato-thalamo-cortical regions and emphasize the importance of parietal regions,” the researchers wrote. “Cortical thickness and surface area represent distinct features of the cortex and may be differentially affected by OCD and possibly moderated by medication status. Further work using longitudinal designs and incorporating genetic and environmental variables will be useful in understanding the precise mechanisms underlying the structural abnormalities preceding the onset of the illness and occurring during the course of the illness.” – by Savannah Demko

Disclosures: Boedhoe reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.