Differences in metabolic network modulation between capsulotomy and deep-brain stimulation for refractory...

Around 7%-10% of patients with obsessive-compulsive disorder (OCD) are refractory to first-line treatment. Neurosurgical approaches are available such as capsulotomy or deep-brain stimulation (DBS). There is strong evidence for central involvement of the corticostriatopallidothalamocortical (CSPTC) circuit in OCD, but the exact mechanism through which these interventions lead to clinical improvement and potential differences in network modulation are not fully understood.

In total, 13 capsulotomy patients (aged 29-59 y, 10 men and 3 women) and 16 DBS patients (aged 25-56 y, 6 men and 10 women) were prospectively included. (18)F-FDG PET was performed before and after capsulotomy and before and after DBS in both stimulation-on and stimulation-off conditions. Presurgical scans were compared with scans of healthy volunteers using SPM8 and global scaling, and metabolic changes after DBS were compared with changes after capsulotomy. Correlations with clinical improvements were investigated using the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and the Hamilton Depression Rating Scale (HAM-D).

Both groups had similar pretreatment clinical morbidity as assessed by Y-BOCS and the Hamilton Depression Rating Scale. Preoperative superior frontal and supplementary motor cortex hypometabolism was common to both patient groups, and the subgenual anterior cingulate, occipital cortex (cuneus), and posterior cerebellum were relatively hypermetabolic. Postoperative metabolic decreases were common to both interventions in the anterior cingulate and the prefrontal and orbitofrontal cortices. Compared with DBS, capsulotomy resulted in more intense metabolic changes, with additional significant decreases in the mediodorsal thalamus, caudate nucleus, and cerebellum as well as increases in the precuneus and the fusiform and lingual gyrus. The stimulation-off condition of DBS patients showed no significant differences from the preoperative state. Improvement in Y-BOCS scores correlated with metabolic changes in the occipital cortex. Baseline metabolism in the subgenual anterior cingulate and superior temporal cortices were related to postoperative improvement of depressive symptoms.

Capsulotomy and DBS lead to similar clinical improvement and similar metabolic network changes in the CSPTC circuit, with a prominent role for the subgenual anterior cingulate and other core structures of the CSPTC. However, metabolic changes are more pronounced and extended in capsulotomy than in DBS. Furthermore, cortical regions outside the CSPTC may also play an important role in OCD symptomatology.