BACKGROUND: Deep brain stimulation (DBS) represents an alternative symptomatic treatment for major depressive disorder in case of failure of pharmacotherapy. The sub-genual cingulate-Brodmann area 25 (CG-25), is one of the most widely used targets for electrode implantation. Given the diverging clinical outcome after DBS, there is a pressing need for in-depth study of brain anatomy and function allowing accurate and reliable prognosis before surgery.
METHODS: We studied five treatment-resistant major depressive disorder patients planned to undergo DBS targeting the CG-25. Before surgery, we acquired high-resolution magnetic resonance (MR) diffusion-weighted images for each patient followed by post-surgery MRI for electrode localization. To estimate individual anatomical connectivity pattern of the active contact location we performed probabilistic diffusion tractography intra-individually. We then correlated connectivity patterns with outcome assessed with standardized clinical tests. Connectivity results were compared between DBS responders and non-responders.
RESULTS: We observed in one patient an excellent clinical response after DBS of the bilateral posterior gyrus rectus rather than the initially targeted CG-25. The remaining four patients with DBS of the CG-25 were considered as non-responders. In the case patient, we demonstrate a strong connectivity of the stimulated regions to the medial prefrontal cortex (mPFC), which contrasted to the lower mPFC connectivity in non-responders.
LIMITATIONS: Confirmation in larger cohorts is needed.
CONCLUSIONS: We propose the posterior gyrus rectus as viable alternative new target for DBS in major depressive disorder. High connectivity between target and mPFC supports the pivotal role of this region in brain networks involved in mood processing.