Effect of deep brain stimulation (DBS) on regional cerebral blood flow (rCBF) in medically-refractory Tourette syndrome (TS)

Objectives In TS, a pathophysiologic role of fronto-subcortical pathways has been discussed. Previous work suggests that DBS of the globus pallidus internus (GPi) and the centromedian-parafascicular/ ventralis oralis internus nuclei of the thalamus (CM/Voi) induces clinical benefit. But the underlying effects on rCBF remain unknown.

Methods 5 severely affected TS pts (age 31±10 yrs, YGTS-Scale 81±8) underwent serial Tc-99m ECD SPECT and were compared to 6 age-matched, healthy controls. In a prospective controlled, randomized, double-blind setting, pts were injected while awake but scanned during anaesthesia: 1. before DBS implantation (preOP) and after 3 mo. of 2. GPi-DBS , 3. CM/Voi-DBS or 4. sham stimulation (OFF). Voxelwise (SMP2, p<0.05) and volumes-of-interest (VOI, SPSS, p<0.01) analysis was performed.

Results In patients preOP compared to controls, rCBF was significantly decreased in the central region, frontal and parietal lobe, specifically in BAs 1, 4-9, 30, 31 and 40. Cerebellar perfusion was increased. DBS significantly decreased rCBF compared to OFF condition: 1. for GPi-DBS in striatum, pallidum, cerebellum and BA21; 2. for CM/Voi-DBS in cerebellum and BA19. A significant increase of rCBF was found during both DBS conditions in the frontal cortex. (Fig. 1)

Conclusions Perfusion of the frontal cortex is reduced in TS, particularly in areas involved in planning and controlling of movements. DBS results in changes of rCBF, which may be correlates of clinical benefit: Reduced perfusion in basal ganglia / cerebellum may reflect reduction of motor-tics; and increased perfusion in frontal cortex may reflect improved motor control