The first large single‐center structural MRI study of OCD was published in 2004 by Pujol et al., based on MRI scans of 72 OCD patients and 72 controls, using voxel‐based morphometry (VBM) (Ashburner & Friston, 2000; Pujol et al., 2004). Compared to healthy controls, OCD patients had, on average, smaller volumes for the medial frontal gyrus, medial orbitofrontal cortex and left insula‐operculum, and greater volumes for the ventral part of the putamen and anterior cerebellum. The striatal finding was mainly driven by older patients and those with longer disease duration. Pujol et al. (2004) also found that although these frontal‐striatal abnormalities were present across the various subtypes of OCD, specific phenotypes showed additional neural alterations: aggressive obsessions and checking compulsions were associated with smaller right amygdala. Subsequently, these effects were largely replicated by the symptom dimension findings of Van den Heuvel et al. (2009).
