| Abstrakt: |
Introduction: The superolateral branch of the medial forebrain bundle (slMFB) is currently investigated as a putative DBS target for the treatment of major depression (MD) and OCD. Diffusion tensor magnetic resonance imaging tractography (DTI FT) assisted targeting is necessary. A total of 24 patients have so far been bilaterally implanted and stimulated for MD at our institutions in two IITs. Here we present a first analysis of this patient cohort focusing on the effectively stimulated fiber tracts and their connections with remote cortical and subcortical network structures via probabilistic DTI FT. Our hypothesis is that subcortical structures that belong to the reward system as well as cortical network structures (especially the prefrontal cortex), responsible for decision-making, goal directed behaviour, planning and mentalizing are affected through effective slMFB DBS (1). Methods: Patient demographics: n = 24, 9f, 29-71 years (47.3 ± 10.5 years). All patients received bilateral DBS electrode through a stereotactic procedure (DBS 3389 model, Medtronic, USA). The procedure has been described in a previous study (2). Imaging data consisted of high-resolution anatomical MRI sequences (3T, Philips Intera, Best, Netherlands, T1W and T2W high resolution images) and 32-direction diffusion tensor imaging. Postoperative helical CT scans were used to delineate electrode positions. The eddy current-induced distortions in diffusion images were corrected using the eddy-correct algorithm in FSL (www.fmrib. ox.ac.uk/fsl). The B0 image was extracted and used as a reference image for the postoperative T2W using FSL linear registration tool, FLIRT. The registered T2W was normalized into MNI space and segmented into GM, WM, and CSF using SPM12 (http:// www.fil.ion.ucl.ac.uk/spm/software/spm12/). The CT was registered into the T2W in the B0 space using FLIRT. The individual effective contact locations were identified. Based on the identified coordinates, a spherical volume of interest (VOI) was created (typically with a radius of 3 mm, representing the volume of activated tissue [VAT]). A displacement field was applied on these VOIs. Probabilistic streamline tractography was performed with MRtrix 3 (http://www.mrtrix.org/). Generated tracks were further employed to convert a 3D image. The group average image was created and smoothed using a Gaussian kernel having a full-width at half-maximum (FWHM) of 4 mm. Results: The clinical results of the patients have in part been presented previously (2). In the present study, a total of 21 data sets had sufficient quality for further evaluation. In all cases only the slMFB and not the inferomedial branch of the medial forebrain bundle (imMFB) where included in the VAT, as expected. On the group level (not normalized), fibers that were affected by DBS connected bilaterally to the nucleus accumbens, the corpus callosum and the medial prefronal cortex (BA 24 and 32). The strongest connection was seen with the rostral prefrontal cortex (BA10) and BA46 (but only before normalizing data). Conclusion: The presented data supports the modulation of a widespread network containing the rostral prefrontal cortex and parts of the forceps minor and the medial prefrontal cortex in slMFB DBS together with subcortical structures of the reward system. BA10 is a unique part of the human brain and has important functions in decision making, multi-tasking and retrieval of episodic memory. Involvement of this region has also been described before with cg25 as target regions (3). BA10 might represent a common denominator for antidepressant efficacy. A combined modulation of the above described cortical and subcortical structures might explain the short and long-term clinical effects that are seen during DBS of the slMFB in MD (2). [ABSTRACT FROM AUTHOR] |
