Medication

Neurosurgery

An Italian center reports their experience with anterior GPi vs. Cm-Pf DBS for TS \citep{32429219}. Forty-one TS patients had DBS in ventro-oralis / centromedian-parafascicular thalamus and 14 had DBS in anteromedial GPi. The authors followed them for 4 years. YGTSS and Y-BOCS improved in both groups (p<.001), but Y-BOCS improved more in the GPi group. Hardware removal was limited to the thalamic DBS group (13/41, vs. 0/14 in the GPi group).
The DBS registry (n=66 bilateral GPi, n=32 centromedian [Cm] thalamus) has provided additional important information \citep{32653920}. Probabilistic tractography from estimated volumes of tissue activated (VTAs) was used to identify networks correlated with improvement in tics or OCD symptoms. Cleverly, these networks were in turn used as seed regions for “reverse” tractography to identify local "hot spots" and "cold spots." For GPi targets, connectivity to limbic and associative networks, caudate, thalamus and cerebellum predicted clinical improvement scores. The anteromedial GPi showed higher connectivity to this network, and the extent to which estimated VTA overlapped with this anteromedial region correlated with tic improvement. For Cm targets, connectivity to sensorimotor and parietal-temporal-occipital networks, putamen and cerebellum correlated with tic improvement. The anterior/lateral part of the Cm region was more highly connected to this network. For both sites, connectivity to prefrontal, orbitofrontal and cingulate cortex correlated with OCD improvement. These results suggest that structural connections of focal stimulation sites to specific networks may lead to clinical benefit. Interestingly, the identified networks may differ not only by symptom but also based on the surgical target region.