Magnetic Resonance Spectroscopy of Brain Circuits in Patients with First-Episode Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is considered neurodevelopmental disorder that shares the feature of dysfunctional frontal-subcortical circuitry, yet the relationship between structural abnormalities or neurobiochemistrical changes and OCD pathogenesis is still unknown. This study aims to use magnetic resonance spectroscopy (MRS) to discover substance-metabolism abnormalities of brain circuits in patients with first-episode OCD, and to study the mechanism of OCD. Twenty patients with first-episode OCD and twenty gender- and age-matched normal controls were studied. Neurochemical abnormalities, including ratios of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho), were measured in the prefrontal cortex, anterior cingulate cortex, orbitofrontal cortex, caudate nucleus, and thalamus with three-dimensional 1H-proton MRS (3D 1H-MRS). The data of the ratios in the two groups were analyzed with a independent samples t-test. Cho/Cr ratios in the thalamus were significantly higher in the first-episode OCD patients than in the controls (P < 0.01), and the NAA/Cr ratios in the caudate nucleus and thalamus were significantly lower in the first-episode OCD patients than in the controls (P < 0.01). However, NAA/Cr ratios in the anterior cingulate cortex and orbitofrontal cortex were higher in the first-episode OCD patients than in the controls (P < 0.01). Distinct neurochemical and histological structure changes (cortico-striatal-thalamic-cortical cycle) exist in patients with first-episode OCD. 1H-MRS is capable of identifying these changes by assessing metabolic abnormalities.