Distinct subcortical volume alterations seen in paediatric, adult OCD patients
There are different patterns of subcortical abnormalities in paediatric and adult patients with obsessive-compulsive disorder (OCD), with the pallidum and hippocampus appearing to be of importance in adult OCD and the thalamus in paediatric OCD, according to results of meta- and mega-analyses.
To identify subcortical brain volumes that vary between OCD and healthy patients, researchers analysed T1 images from 1,830 OCD patients and 1,759 control participants using coordinated and standardized processing.
A meta-analysis was performed on the mean of the left and right hemisphere measures of each subcortical structure, and a mega-analysis was conducted by pooling these volumetric measurements from each site. Additionally, researchers assessed potential modulating effects of clinical characteristics on morphological differences in OCD patients.
Based on the meta-analysis, adult patients had significantly smaller hippocampal volumes (Cohen’s d=−0.13; % difference=−2.80) and larger pallidum volumes (d=0.16; % difference=3.16) compared with adult controls. Both effects were stronger in medicated patients than in controls (d=−0.29; % difference=−4.18; and d=0.29; % difference=4.38, respectively).
Furthermore, significantly larger thalamic volumes (d=0.38; % difference=3.08) were seen in unmedicated paediatric patients than in paediatric controls.
None of these findings were mediated by sample characteristics, such as mean age or scanning field strength. The mega-analysis generated similar results.
A previous study revealed that OCD patients had significantly smaller volumes of frontal gray and white matter bilaterally, including the dorsomedial prefrontal cortex, the anterior cingulate cortex and the inferior frontal gyrus extending to the anterior insula. Furthermore, patients showed greater cerebellar gray matter volume bilaterally than healthy participants. [Am J Psychiatry 2014;171:340-9]
According to researchers, the findings of the current study stress the potential importance of neurodevelopmental changes in OCD, and that further research on neuroplasticity in OCD may be useful.