Introduction: Stereotactic cingulotomy has been used to treat severe, refractory obsessive-compulsive disorder (OCD) for decades.[1] However, while cingulotomy is believed to disrupt reentrant fronto-striato-thalamic circuitry (FSTC), how cingulotomy modifies this circuit is unknown.[2] We retrospectively analyzed preoperative and postoperative neuroimaging, using diffusion tensor imaging (DTI) and voxel based morphometry (VBM) techniques, in patients who underwent cingulotomy for OCD, to determine how non-lesioned sites adapted postoperatively.

Methods: Five patients were selected who received preoperative and one year postoperative volumetric T1 images. For each patient, whole brain gray matter partial volume changes were calculated in MNI standard space using the FSL VBM toolkit.[3,4] Results were cluster thresholded for significance using the FSL program easythresh. Additionally, four patients were selected who received diffusion tensor imaging both one year postoperatively, and either immediately before or after the surgery. FSL's tract based spatial statistics (TBSS) toolkit was used to construct patient specific fractional anisotropy skeletons, and the mean fractional anisotropy (FA) of the left and right anterior internal capsule was analyzed over time on a patient-specific basis.[5]

Results: A significant gray matter volume reduction occurring over the postoperative year was seen for all patients in a right-sided cluster spanning the dorsolateral prefrontal, superior frontal and paracingulate cortex (figure 1, p = 0.008, corrected for multiple comparisons by threshold free cluster analysis.). Anterior internal capsule FA changes were then plotted for each of the four patients (Figure 2, 3). Compared to preoperative FA, a postoperative decrease in FA was seen in all patients at all time points in the right anterior internal capsule. While there were some decreases in FA on the left, this was not consistent across subjects.

Conclusions: Cingulotomy results in secondary alterations of the right prefrontal cortex and right anterior internal capsule, which develop within one year of surgery. These findings suggest that post-operative plasticity may account for some of the therapeutic effects of cingulotomy. Increased understanding of these circuits will assist with the development of novel therapies for OCD.

Patient Care: By describing the plasticity secondary to cingulotomy, a procedure known to be effective in select patients for treating severe refractory obsessive-compulsive disorder, we hope to contribute to the discussion of how neurosurgical techniques can best be utilized for treating severe refractory psychiatric disorders. Furthermore, these insights may aid in development of novel, less invasive therapies for OCD targeting these circuits. Additionally, by highlighting the potential use of neuroimaging analysis techniques, we hope to bolster the neuroimaging knowledge base of the stereotactic and functional community so further analyses can be undertaken to study post-operative plasticity.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the role of the fronto-striato-thalamic circuitry in obsessive-compulsive disorder. 2) Understand the uses of neuroimaging analysis in elucidating postoperative plasticity after stereotactic lesioning. 3) Describe how the fronto-striato-thalamic circuitry adapts in the postoperative period after bilateral thermal lesioning of the dorsal anterior cingulate.

References: 1. Sheth, Sameer A., et al. "Limbic system surgery for treatment-refractory obsessive-compulsive disorder: a prospective long-term follow-up of 64 patients: Clinical article." Journal of neurosurgery 118.3 (2013): 491-497. 2. Chiu, Chen-Huan, et al. "White matter abnormalities of fronto-striato-thalamic circuitry in obsessive–compulsive disorder: A study using diffusion spectrum imaging tractography." Psychiatry Research: Neuroimaging 192.3 (2011): 176-182. 3. Li, Mingli, et al. "Voxel-based morphometric analysis on the volume of gray matter in bipolar I disorder." Psychiatry Research: Neuroimaging 191.2 (2011): 92-97. 4. Douaud, Gwenaëlle, et al. "Anatomically related grey and white matter abnormalities in adolescent-onset schizophrenia." Brain 130.9 (2007): 2375-2386. 5. Smith, Stephen M., et al. "Tract-based spatial statistics: voxelwise analysis of multi-subject diffusion data." Neuroimage 31.4 (2006): 1487-1505.