Figure 8.

Fiber tract reconstruction of OFC-thalamic connections using two-tensor diffusion tractography in the right (A) and left (B) hemispheres of a patient with OCD who had DBS neurosurgery bilaterally. The two fiber tracts are lOFC-thal (in red) and mOFC-thal (in blue). Their morphology resembles that of a “cloud” containing intertwined fibers of both tracts running side-by-side in the VC/VS region, which poses the question of how anatomically specific the target engagement by an electrode contact can be. A contact in zone 1 in the left hemisphere (E) and in zones 1 and 2 in the right hemisphere (B) would stimulate both lOFC-thal (red) and mOFC-thal (blue) fibers. By contrast, a contact in zone 2 of the left hemisphere (E) would stimulate fibers of lOFC-thal (red) only. Contacts 0 and 1 in both hemispheres (C-right, F-left) were situated in regions containing both lOFC-thal and mOFC-thal fibers. Contact 2 in both hemispheres (C-right, F-left) and contact 3 in the right hemisphere (C) engaged only lOFC-thal fibers, whereas contact 3 in the left hemisphere (F) engaged only mOFC-thal fibers. Panels G, H and I show post-implantation CT scans with electrodes and depict the center of mass line (COM line) representation of the lOFC-thal (in red) and mOFC-thal (in blue) fiber tracts and their spatial relationships with the electrode implant in augmented visualizations in 3-D (panel H) and 2-D (I). R = right; L = left; numbers 0, 1, 2 and 3 represent the four contacts of the lead.