Exploring the clinical outcomes after deep brain stimulation in Tourette syndrome

Introduction: Deep brain stimulation (DBS) of the thalamic centromedian-parafascicular (CM-Pf) region is the most common target to treat refractory Tourette syndrome (TS), but the improvement among the patients is quite variable. This study describes the outcomes of stimulation in TS patients and attempts to determine whether the volume of tissue activated (VTA) inside the thalamus or the structural connectivity between the area stimulated and different regions of the brain is associated with tic improvement.

Methods: The DBS patient response was measured as the percentage change in the Yale Global Tic Severity Scale (YGTSS) before and 12 months after surgery. The sum of the two overlapping VTA/CM-Pf volumes from both hemispheres was correlated with the percent change in YGTSS scores to assess whether the area stimulated inside the CM-Pf affects the clinical outcome. Structural connectivity estimates between the VTA (of each patient) and different regions of the brain were computed using a normative connectome that was taken from healthy subjects.

Results: Five male patients aged 26.8 ± 9.3 years were included. No relationships were found between the areas stimulated and the changes in patient tics (p = .374). However, the right frontal middle gyrus (R = 0.564, p = .03), the left frontal superior sulci region (R = 0.900, p = .030) and the left cingulate sulci region (R = 0.821, p = .045) structurally correlated with tic improvement.

Conclusion: These data suggests that the volume of thalamic area that is stimulated does not explain the variance in outcomes in TS, however, the pattern of connectivity between the region stimulated and specific brain cortical areas is linked to patient outcome.