Distance to white matter trajectories is associated with treatment response to internal capsule deep brain stimulation in treatment-refractory depression

Abstract

Highlights Stimulation closer to tracts was associated with better outcome in DBS for depression. Lead placement was consistent across (non)responders w.r.t. anatomical landmarks. Tractography-guided surgery needed to ensure tracts lie within activated tissue.

White Matter Microstructure Associated with the Antidepressant Effects of Deep Brain Stimulation in Treatment-Resistant Depression: A Review of Diffusion Tensor Imaging Studies

“…The sample size ranged from 2 [ 32 ] to 24 [ 33 ] patients. Seven studies [ 22 , 24 , 26 , 27 , 34 , 35 , 36 ] included only patients with MDD, while one study [ 37 ] assessed both patients with MDD and bipolar disorder (BD). Three studies [ 32 , 33 , 38 ] did not specify the type of underlying disorder.…”

“…The majority of included studies applied DBS to the sgCC [ 32 , 34 , 35 , 36 , 37 ] or medial forebrain bundle [ 22 , 27 , 33 ]. The remaining investigations applied DBS to the ventral capsule/ventral striatum [ 38 ], posterior rectus gyrus [ 26 ], and ventral anterior limb of the internal capsule [ 24 ]. The methods and key findings of the studies are detailed in Table 1 .…”

“…Except for one study [ 24 ], the others used 3T MRI machines with a b-value of 1000. They all applied tractography ( Table 1 ).…”

“…They all applied tractography ( Table 1 ). Overall, the investigations used four major approaches to conduct tractography: (a) seed-to-target probabilistic tractography between pre-defined target regions and patient-specific volume of activated tissue (VAT) [ 32 , 34 , 36 ], defined as the spatial extent of the electrical field delivered by the lead to the anatomical structures near the selected target [ 43 , 44 ]; (b) whole-brain probabilistic tractography with VAT as the seed [ 22 , 27 , 35 , 37 , 38 ]; (c) bundle-specific tractography, considering some specific WM tracts for the analysis [ 24 , 33 , 35 ]; (d) whole-brain unconstrained probabilistic tractography [ 26 ].…”

“…The exact mechanism of DBS is still unknown, although it has been hypothesized that the suppression of gamma oscillations and facilitation of theta-gamma coupling by DBS is mediated by both sgCC activation of inhibitory circuits and an increase in plasticity in the frontal cortex [ 20 ], ultimately leading to the normalization of abnormal network connectivity [ 21 ]. Furthermore, in recent years, the results from diffusion tensor imaging (DTI) provided a useful tool not only in the definition of surgical targets for DBS [ 22 , 23 ], but also in the study of WM tracts in relation to treatment response [ 24 ] This is because DTI provides useful information on the orientation and integrity of white matter (WM) tracts in TRD [ 25 ], and allows us to investigate the changes in WM and connectivity between frontal and subcortical structures following DBS [ 26 , 27 ]. It is a relatively sensitive neuroimaging technique that assesses water molecule diffusion in extracellular space within the tissue, and has the potential to provide useful information regarding alterations in the microstructure of the WM [ 28 ].…”