Parietal white matter abnormalities in obsessive–compulsive disorder: a magnetic resonance spectroscopy study at 3‐Tesla

Objective: To identify a neurochemical basis for the hypothesis that an aberrant cortico‐subcortical circuit underlies obsessive–compulsive disorder (OCD). The white matter was also investigated because of recent research which suggests the altered connectivity of axons. Method: Using 3‐Tesla magnetic resonance spectroscopy, the relative concentrations of N ‐acetylaspartate (NAA) and choline‐containing compounds (Cho) to creatine/phosphocreatine (Cr) were measured in the anterior cingulate, basal ganglia, thalamus, frontal and parietal white matter of 12 OCD patients, and 32 control subjects. Results: The mean concentration of Cho/Cr was significantly higher in the patients than in the controls, but only in the parietal white matter, while no significant group differences in NAA/Cr were observed in any of the brain regions. Parietal Cho/Cr correlated positively with the severity of OCD symptoms. Conclusion: This finding provides indirect evidence for the parietal white matter involvement in OCD, thus suggesting a change in the phospholipids of myelinated axons and/or glia cells.