Diffusion Tensor Imaging to Aid Subgenual Cingulum Target Selection for Deep Brain Stimulation in Depression

Abstract

Background: The most investigated target for deep brain stimulation in depression is the subgenual cingulate gyrus (Cg25) which has been shown to be a critical hub for signalling in the condition. Diffusion tensor imaging (DTI) is a form of MR sequence that can visualise white matter connections and potentially aid target selection. Objectives: To assess whether targets selected using DTI to find the area of maximal tract crossover (maximal isotropy) underlying the subgenual cingulum differ significantly in location from those selected using standard T₂ sequences. Methods: Fifty-nine non-depressed adult volunteers underwent MR imaging using T₁, T₂ and DTI sequences of the brain. Each patient had targets selected for both hemispheres using both T₂ and DTI sequences. The significance of the differences in coordinates in all three dimensions was tested using the paired t test. Results: There was a significant difference in the mediolateral (x) and dorsoventral (z) coordinates of DTI targets when compared with T₂ targets (p < 0.001). Conclusions: Targets within Cg25 selected using DTI are significantly different in location from those selected using T₂ sequences and have the potential to enhance treatment outcome by reducing the impact of interindividual variability.

Diffusion Tensor Imaging Investigation of Uncinate Fasciculus Anatomy in Healthy Controls: Description of a Subgenual Stem

“…Johansen-Berg et al [21] demonstrated that the white matter connections that were likely activated in DBS responders differed in location and distribution to those in nonresponders, with the responder group activating (amongst others) white matter fibers extending from BA25 towards the amygdala and anterior temporal pole. The presence of these fibers was also confirmed by our prior published work on target selection for DBS using diffusion tensor imaging (DTI) [27]. By anatomical necessity, these fibers would run in close proximity to the subinsular/subcaudate body of the UF and would also curve in a hook-shaped manner around the posterior insula to reach the mesial temporal structures.…”

“…Based on the anatomical proximity of these fibers to the UF as well as the demonstrated reduced connectivity of the UF in depressed patients [6,7,27], we hypothesize that these fibers are in fact a medial/subgenual prefrontal stem of the UF, and that there are 3 rather than 2 prefrontal stems of the UF. We have tested this hypothesis using DTI, a noninvasive indirect method of imaging white matter fibers with magnetic resonance imaging (MRI) founded on the tendency of water molecules to diffuse parallel rather than perpendicularly to the long axis of white matter tracts.…”

“…Prior studies on the white matter tracts underlying the subgenual cingulate gyrus (BA25) have demonstrated the presence of fibers extending towards the amygdala [21,22,27,30] and that these fibers are amongst those likely activated in responders rather than nonresponders to DBS of BA25 [19,21,22]. In fact, Riva-Posse et al [19] demonstrated that the volume of activated tissue in BA25 DBS responders consistently involved fibers of the UF using seed tractography of an activated tissue model ROI [30].…”

Optimizing Prelemniscal Radiations as a Target for Motor Symptoms in Parkinson's Disease Treatment

“…Anatomical studies for subthalamic cerebellar-thalamic fibers [27] and frontal subgenual fibers [28] have demonstrated individual variations in the position of fiber tracts that for the subgenual area correlate with a decreased response to DBS in patients with treatment-resistant emotional depression [29], and variation of electrode contact positions in regard to cerebellar-thalamic fibers correlates with improvement of tremor in Vim-DBS [30]. With that hypothesis in mind, we performed an ultraselective MRI-DTI analysis of Raprl in 5 cases and confirmed in a preliminary report that its fiber component includes the following: (1) cerebellar fibers travelling in the brachium conjunctivum to the contralateral Raprl; (2) a second component from the globus pallidus internus traveling in the ansa lenticularis beyond Forel's fields towards the dorsal brain stem (in the brain stem, these fibers travel in the space between the voxels corresponding to the medial lemniscus and brachium conjunctivum, where the pedunculopontine nucleus is located), and (3) a third component connecting the mesencephalon with the orbitofrontal cortex [31] (fig.…”

Integrating Diffusion Tensor Imaging-Based Tractography into Deep Brain Stimulation Surgery: A Review of the Literature

“…Studies are scarce so far, but they have provided data that, if confirmed, may be useful to optimize DBS surgery. White matter tracts such as the DRT and the MFB have been identified as potential targets for stimulation for tremor and depression, respectively [14,20,24,28,42,43,52,53]. The selection of optimal subregions within the usual targets, based on their connections with other brain areas, has advanced as well for the treatment of abnormal movements and pain [3,18,20,50].…”