Functional neuroimaging of an unmedicated patient with OCD most classically demonstrates which of the following patterns?

• A Hypometabolism confined to the medial temporal lobe
• B Hypermetabolism in the orbitofrontal cortex and head of the caudate nucleus ✓
• C Selective atrophy of the cerebellar vermis
• D Reduced activity in the dorsolateral prefrontal cortex only

Explanation

OCD is linked to overactivity of the cortico-striato-thalamo-cortical loop, and imaging shows increased metabolic activity in the orbitofrontal cortex and the head of the caudate nucleus. Notably, successful treatment with either an SSRI or cognitive behavioural therapy reduces this caudate hypermetabolism, supporting the model that both interventions act on the same circuit. Medial temporal hypometabolism suggests Alzheimer disease, and vermian atrophy is not an OCD finding.

Reference: Kaplan and Sadock's Synopsis of Psychiatry, 11th ed.

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