Widespread structural brain changes in OCD: a systematic review of voxel-based morphometry studies.

Area of Science:

• Neuroscience
• Neuroimaging
• Psychiatry

Background:

• The traditional model of obsessive-compulsive disorder (OCD) implicates the "affective circuit" with reduced gray matter in specific prefrontal and temporolimbic regions and enlarged striatal and thalamic volumes.
• Whole-brain voxel-based morphometry (VBM) studies suggest broader brain region involvement in OCD beyond the orbitofronto-striatal circuit.
• Previous findings may be limited by methodological variations, medication status, and comorbidities.

Purpose of the Study:

• To systematically review whole-brain VBM literature on OCD, focusing on consistency, replication, and the relationship between clinical variables and brain anatomy.
• To determine if OCD-related brain alterations extend beyond the established "affective" circuit.
• To investigate the network-level basis of OCD neurobiology.

Main Methods:

• Systematic review of PubMed database searches up to February 2012.
• Inclusion criteria focused on whole-brain VBM studies of OCD, yielding 18 studies.
• Analysis included 511 patients with OCD and 504 healthy controls.

Main Results:

• Consistent evidence supports widespread structural brain abnormalities in OCD, indicating a network-level dysfunction.
• Reduced gray matter volume was observed in prefrontal cortical regions of the "executive" circuit (dorsomedial, dorsolateral, ventrolateral, frontopolar) and temporo-parieto-occipital associative areas.
• Increased internal capsule volume and reduced frontal/parietal white matter suggest altered anatomical connectivity within fronto-subcortical circuits.
• Morphometric changes in both "affective" and "executive" circuits correlate with the disease's clinical course and symptom severity.

Conclusions:

• Obsessive-compulsive disorder (OCD) involves a more extensive network of cerebral dysfunctions than previously recognized.
• Structural abnormalities in both "affective" and "executive" brain circuits contribute to neurobiological vulnerability and explain clinical heterogeneity in OCD.
• These findings highlight the importance of considering network-level alterations in understanding OCD pathophysiology and treatment approaches.