Radiology: MRI reveals brain abnormalities in OCD patients
MRIs of patients with obsessive-compulsive disorder (OCD) show corpus callosum and white matter abnormalities in the brain, with heightened differences observed in individuals with more severe OCD symptoms, leading the authors of a study published in the July issue of Radiology to suggest the possibility of improved management of OCD patients using MRI.
OCD is a psychiatric disorder characterized by anxiety-inducing thoughts and impulses that are typically persistent and inappropriate, which patients then seek to attenuate by performing rituals and repetitive behaviors. As many as 2 to 3 percent of persons worldwide have OCD, for which early studies have pointed to potential white matter abnormalities, although “published findings have been varied and even contradictory,” according to Fei Li, PhD, and co-authors from the department of radiology at Huaxi MR Research Center at West China Hospital of Sichuan University, in Sichuan, China.
Li and colleagues used diffusion-tensor MRI (3.0T) to compare whether OCD patients showed abnormal fractional anisotropy (FA) and axial and radial diffusivity differences from healthy controls. Twenty-three patients in each group underwent imaging, with the OCD group’s results evaluated according to the severity of symptoms, based on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS).
Voxel-based analysis showed significantly increased FA among OCD patients in the genu and body of the corpus callosum, as well as in the white matter of the right superior frontal gyrus.
The mean FA in the genu and body of the corpus callosum measured 0.499 in the OCD group, compared with 0.446 among controls. Mean white matter FA in the right superior frontal gyrus reached 0.411 in the OCD group, versus 0.375 for controls.
In the increased FA areas, axial diffusivity was likewise higher in OCD patients for both the genu and the body of the corpus callosum and right superior frontal white matter, although radial diffusivity did not differ between the two groups.
The authors also found a moderate but significant correlation between FA in the white matter of the left middle temporal gyrus and patients’ Y-BOCS total score as well as obsessive subscale score (r = 0.542 and 0.400, respectively). Li and colleagues interpreted these findings as suggesting that the white matter of the temporal lobe may play a role in OCD pathology.
“We therefore suggest that deficits of specific white matter within the cortical-striatal-thalamic-cortical circuit may be pathophysiologically significant in OCD and also account for the increased axial diffusivity and FA that we observed.”
In failing to confirm previous evidence that suggested a significant role for the frontal-subcortical circuits in OCD pathophysiology and symptoms, Li and co-authors speculated that the white matter of frontal regions may not, in fact, play an important role in determining clinical status.
Considering both their study’s small sample size and the use of medication in a number of the OCD patients, the authors called for additional studies with larger cohorts and unmedicated subjects.
“Nevertheless, our results suggest the potential clinical utility of the [diffusion-tensor] changes as a useful marker, which may help monitor disease progression and consequently may inform timely clinical intervention,” Li and co-authors concluded.
OCD is a psychiatric disorder characterized by anxiety-inducing thoughts and impulses that are typically persistent and inappropriate, which patients then seek to attenuate by performing rituals and repetitive behaviors. As many as 2 to 3 percent of persons worldwide have OCD, for which early studies have pointed to potential white matter abnormalities, although “published findings have been varied and even contradictory,” according to Fei Li, PhD, and co-authors from the department of radiology at Huaxi MR Research Center at West China Hospital of Sichuan University, in Sichuan, China.
Li and colleagues used diffusion-tensor MRI (3.0T) to compare whether OCD patients showed abnormal fractional anisotropy (FA) and axial and radial diffusivity differences from healthy controls. Twenty-three patients in each group underwent imaging, with the OCD group’s results evaluated according to the severity of symptoms, based on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS).
Voxel-based analysis showed significantly increased FA among OCD patients in the genu and body of the corpus callosum, as well as in the white matter of the right superior frontal gyrus.
The mean FA in the genu and body of the corpus callosum measured 0.499 in the OCD group, compared with 0.446 among controls. Mean white matter FA in the right superior frontal gyrus reached 0.411 in the OCD group, versus 0.375 for controls.
In the increased FA areas, axial diffusivity was likewise higher in OCD patients for both the genu and the body of the corpus callosum and right superior frontal white matter, although radial diffusivity did not differ between the two groups.
The authors also found a moderate but significant correlation between FA in the white matter of the left middle temporal gyrus and patients’ Y-BOCS total score as well as obsessive subscale score (r = 0.542 and 0.400, respectively). Li and colleagues interpreted these findings as suggesting that the white matter of the temporal lobe may play a role in OCD pathology.
“We therefore suggest that deficits of specific white matter within the cortical-striatal-thalamic-cortical circuit may be pathophysiologically significant in OCD and also account for the increased axial diffusivity and FA that we observed.”
In failing to confirm previous evidence that suggested a significant role for the frontal-subcortical circuits in OCD pathophysiology and symptoms, Li and co-authors speculated that the white matter of frontal regions may not, in fact, play an important role in determining clinical status.
Considering both their study’s small sample size and the use of medication in a number of the OCD patients, the authors called for additional studies with larger cohorts and unmedicated subjects.
“Nevertheless, our results suggest the potential clinical utility of the [diffusion-tensor] changes as a useful marker, which may help monitor disease progression and consequently may inform timely clinical intervention,” Li and co-authors concluded.