Objective: Recent epidemiological and clinical data suggest that obsessive-compulsive disorder (OCD) may be subtyped according the age of onset of obsessive-compulsive symptoms. The regional cerebral blood flow (rCBF) single photon emission computed tomography (SPECT) technique was used to investigate whether the pathophysiology of OCD differs between early- and late-onset OCD subjects.
Method: Resting rCBF was measured in 13 early-onset (<10 years) and 13 late-onset (>12 years) adult OCD subjects and in 22 healthy controls. Voxel-based rCBF comparisons were performed with statistical parametric mapping.
Results: Early-onset OCD cases showed decreased rCBF in the right thalamus, left anterior cingulate cortex, and bilateral inferior prefrontal cortex relative to late-onset subjects (p < .0005, uncorrected for multiple comparisons). Relative to controls, early-onset cases had decreased left anterior cingulate and right orbitofrontal rCBF, and increased rCBF in the right cerebellum, whereas late-onset subjects showed reduced right orbitofrontal rCBF and increased rCBF in the left precuneus. In early-onset subjects only, severity of obsessive-compulsive symptoms correlated positively with left orbitofrontal rCBF.
Conclusions: rCBF differences in frontal-subcortical circuits between early-onset and late-onset OCD subjects were found, both in location and direction of changes. These results provide preliminary evidence that brain mechanisms in OCD may differ depending on the age at which symptoms are first expressed.