DTI-based deterministic fibre tracking of the medial forebrain bundle

Dear Editor, We would like to thank Josue M. Avecillas-Chasin for his appreciation of our study BThe variability of atlas-based targets in relation to surrounding major fibre tracts in thalamic deep brain stimulation^[1] and for his valuable comments on the study.We fully agree with the concerns regarding the limitations of tractography, as already discussed in our article [1] and earlier reports by our group [2,6,10]. His own work constitutes a further valuable contribution to the topic [3]. Several studies in the past have used diffusion tensor imaging (DTI) and tractography to visualise fibre tracts in the region of the ventro-lateral thalamus [5,7,8,11]. However the reliability of the depicted connections is yet unclear. First approaches to comparing diffusion tensor imaging-based fibre tracts with clinical effects have been made [3-5, 10] and have shown promising results. But, as demanded by Avecillas-Chasin, the method needs to be optimised and standardised. Optimal parameters for data acquisition (number of read-out directions, field strengths of MR scanner or voxel size) have to be generated, as well as optimal algorithms such as a mixture of tensors, Q-ball imaging, diffusion spectrum imaging and others [10]. As also mentioned by Avecillas-Chasin, it will be necessary in the future to compare deterministic algorithms with the probabilistic method, especially in tracts such as the dentate-rubro-thalamic tract (DRTT) that intersect regions with multiple fibre orientations. Furthermore, different software packages lead to different results in the depiction of chosen fibre tracts [6].We are aware that the used method of DTI with deterministic tractography has its limitations and is not yet elaborate and reliable enough for implementation in routine clinical use as a standard tool. Therefore, today we still depend on neurophysiological and clinical information for targeting by means of micro-electrode recording (MER) and clinical testing in the setting of awake-surgeries [9]. Conflict of interest None. References 1. Anthofer J, Steib K, Fellner C, Lange M, Brawanski A, Schlaier J (2014) The variability of atlas-based targets in relation to surrounding major fibre tracts in thalamic deep brain stimulation. Acta Neurochir 156:1497-1504, discussion 1504 2. Anthofer JM, Steib K, Fellner C, Lange M, Brawanski A, Schlaier J (2015) DTI-based deterministic fibre tracking of the medial forebrain bundle. Acta Neurochir 157:469-477 3. Avecillas-Chasin JM, Alonso-Frech F, Parras O, Del Prado N, Barcia JA (2015) Assessment of a method to determine deep brain stimulation targets using deterministic tractography in a navigation system. Neurosurg Rev.

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supporting

confidence: 89%

“…We fully agree with the concerns regarding the limitations of tractography, as already discussed in our article [1] and earlier reports by our group [2,6,10]. His own work constitutes a further valuable contribution to the topic [3].…”

supporting

confidence: 89%

Letter of response to “Individualization of deep brain stimulation targets for movement disorders”

et al. 2015

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“…Since its first description (Coenen et al, 2009), the use of DTI- based tractography has typically used a volume of interested that was placed just lateral to the ventral tegmental area (Anthofer et al, 2015; Coenen et al, 2009; Coenen et al, 2012; Coenen et al, 2018; Fenoy et al, 2016; Schlaepfer et al, 2013). In that sense, the seed region for the local tractographic approach is the same as the effectively targeted and stimulated region.…”

Section: Discussionmentioning

confidence: 99%

“…While on the group level DT might be able to show most of these distant projections (Coenen et al, 2012), on the single subject level this is typically not possible (Anthofer et al, 2015; Hana et al, 2015) even when using advanced software solutions (Anthofer et al, 2015; Coenen et al, 2018). Advanced tracking methodology including multi-shell imaging and holistic tractography approaches are able to show the complete extension of the slMFB (Coenen et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Tractography-assisted deep brain stimulation of the superolateral branch of the medial forebrain bundle (slMFB DBS) in major depression

Coenen

Sajonz

Reisert

et al. 2018

NeuroImage: Clinical

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BackgroundDeep brain stimulation (DBS) of the superolateral branch of the medial forebrain bundle (slMFB) emerges as a - yet experimental - treatment for major depressive disorder (MDD) and other treatment refractory psychiatric diseases. First experiences have been reported from two open label pilot trials in major depression (MDD) and long-term effectiveness for MDD (50 months) has been reported.ObjectiveTo give a detailed description of the surgical technique for DBS of the superolateral branch of the medial forebrain bundle (slMFB) in MDD.MethodsSurgical experience from bilateral implantation procedures in n = 24 patients with MDD is reported. The detailed procedure of tractography-assisted targeting together with detailed electrophysiology in 144 trajectories in the target region (recording and stimulation) is described. Achieved electrode positions were evaluated based on postoperative helical CT and fused to preoperative high resolution anatomical magnetic resonance imaging (MRI; Philips Medical Systems, Best, Netherlands), including the pre-operative diffusion tensor imaging (DTI) tractographic information (StealthViz DTI, Medtronic, USA; Framelink 5.0, Medtronic, USA). Midcommissural point (MCP) coordinates of effective contact (EC) location, together with angles of entry into the target region were evaluated. To investigate incidental stimulation of surrounding nuclei (subthalamic nucleus, STN; substantia nigra, SNr; and red nucleus, RN) as a possible mechanism, a therapeutic triangle (TT) was defined, located between these structures (based on MRI criteria in T2) and evaluated with respect to EC locations.ResultsBilateral slMFB DBS was performed in all patients. We identified an electrophysiological environment (defined by autonomic reaction, passive microelectrode recording, acute effects and oculomotor effects) that helps to identify the proper target site on the operation table. Postoperative MCP-evaluation of effective contacts (EC) shows a significant variability with respect to localization. Evaluation of the TT shows that responders will typically have their active contacts inside the triangle and that surrounding nuclei (STN, SNr, RN) are not directly hit by EC, indicating a predominant white matter stimulation. The individual EC position within the triangle cannot be predicted and is based on individual slMFB (tractography) geometry. There was one intracranial bleeding (FORESEE I study) during a first implantation attempt in a patient who later received full bilateral implantation. Typical oculomotor side effects are idiosyncratic for the target region and at inferior contacts.ConclusionThe detailed surgical procedure of slMFB DBS implantation has not been described before. The slMFB emerges as an interesting region for the treatment of major depression (and other psychiatric diseases) with DBS. So far it has only been successfully researched in open label clinical case series and in 15 patients published. Stimulation probably achieves its effect through direct white-matter modulation of slMFB...

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“…Several targets have been implicated in treatment resistant depression (TRD) including subgenual cingulate cortex (SCC), nucleus accumbens (NAcc), ventral capsule/ventral striatum (VA/VS), lateral habenula (LHb), inferior thalamic peduncle (ITP), and the medial forebrain bundle (MFB) (Bewernick and Schlaepfer, 2013, Malone et al, 2009, Holtzheimer et al, 2012, Lozano et al, 2008, Sartorius and Henn, 2007, Coenen et al, 2011). More recently, the use of diffusion tensor imaging (DTI) based fiber tracking has heightened interest in anatomical targeting of white matter tracts that have been implicated in disease states like TRD (Schoene-Bake et al, 2010, Anthofer et al, 2015). Stimulation of the supero-lateral branch of the medial forebrain bundle (slMFB), a white matter tract that interconnects various centers of the reward pathway including the NAcc, ventral tegmental area (VTA), hypothalamus, and amygdala has shown promising results in the treatment of TRD and has spurred interest in the identification and stimulation of other white matter tracts involved in the pathophysiology of TRD (Coenen et al, 2009, Coenen et al, 2011, Coenen et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Identification of the stria medullaris thalami using diffusion tensor imaging

Kochanski

Dawe

Eddelman

et al. 2016

NeuroImage: Clinical

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BackgroundDeep brain stimulation (DBS) via anatomical targeting of white matter tracts defined by diffusion tensor imaging (DTI) may be a useful tool in the treatment of pathologic neurophysiologic circuits implicated in certain disease states like treatment resistant depression (TRD). We sought to determine if DTI could be used to define the stria medullaris thalami (SM), the major afferent white matter pathway to the lateral habenula (LHb), a thalamic nucleus implicated in the pathophysiology of TRD.MethodsProbabilistic DTI was performed on ten cerebral hemispheres in five patients who underwent preoperative MRI for DBS surgery. Manual identification of the LHb on axial T1 weighted MRI was used for the initial seed region for tractography. Variations in tractography depending on chosen axial slice of the LHb and chosen voxel within the LHb were also assessed.ResultsIn all hemispheres the SM was reliably visualized. Variations in chosen axial seed slice as well as variations in single seed placement did not lead to significant changes in SM tractography.ConclusionsProbabilistic DTI can be used to visualize the SM which may ultimately provide utility for direct anatomic targeting in DBS surgery.

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DTI-based deterministic fibre tracking of the medial forebrain bundle

Abstract: Deterministic fibre tracking with standardised ROIs provides constant and reproducible delineations of the medial forebrain bundle. Its visualisation might help to adjust targeting in DBS for psychiatric disorders.

Cited by 32 publications

References 39 publications

Letter of response to “Individualization of deep brain stimulation targets for movement disorders”

Letter of response to “Individualization of deep brain stimulation targets for movement disorders”

Tractography-assisted deep brain stimulation of the superolateral branch of the medial forebrain bundle (slMFB DBS) in major depression

Identification of the stria medullaris thalami using diffusion tensor imaging

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