Validation of diffusion tensor imaging tractography to visualize the dentatorubrothalamic tract for surgical planning

Abstract

OBJECTIVE The dentatorubrothalamic tract (DRTT) has been suggested as the anatomical substrate for deep brain stimulation (DBS)-induced tremor alleviation. So far, little is known about how accurately and reliably tracking results correspond to the anatomical DRTT. The objective of this study was to systematically investigate and validate the results of different tractography approaches for surgical planning. METHODS The authors retrospectively analyzed 4 methodological approaches for diffusion tensor imaging (DTI)-based fiber tracking using different regions of interest in 6 patients with essential tremor. Tracking results were analyzed and validated with reference to MRI-based anatomical landmarks, were projected onto the stereotactic atlas of Morel at 3 predetermined levels (vertical levels -3.6, -1.8, and 0 mm below the anterior commissure-posterior commissure line), and were correlated to clinical outcome. RESULTS The 4 different methodologies for tracking the DRTT led to divergent results with respect to the MRI-based anatomical landmarks and when projected onto the stereotactic atlas of Morel. There was a statistically significant difference in the lateral and anteroposterior coordinates at the 3 vertical levels (p < 0.001, 2-way ANOVA). Different fractional anisotropy values ranging from 0.1 to 0.46 were required for anatomically plausible tracking results and led to varying degrees of success. Tracking results were not correlated to postoperative tremor reduction. CONCLUSIONS Different tracking methods can yield results with good anatomical approximation. The authors recommend using 3 regions of interest including the dentate nucleus of the cerebellum, the posterior subthalamic area, and the precentral gyrus to visualize the DRTT. Tracking results must be cautiously evaluated for anatomical plausibility and accuracy in each patient.

Microstructural changes of the dentato‐rubro‐thalamic tract after transcranial MR guided focused ultrasound ablation of the posteroventral VIM in essential tremor

“…Thalamotomy for tremor is aimed to impact on the anatomical connections within the cerebello‐thalamo‐cortical system, specifically the DRTT, stopping the tremor activity from propagating from the cerebellum to the motor cortex. Using tractography it is possible to define the anatomical boundaries of this tract (Akram et al, ; Meola, Yeh, Fellows‐Mayle, Weed, & Fernandez‐Miranda, ; Nowacki, Schlaier, Debove, & Pollo, ), and so the number of studies encouraging the tractography‐based segmentation of the DRTT for targeting in either thalamotomy or DBS is growing (Akram et al, ; Coenen et al, ; Sammartino et al, ; Tian et al, ; Tsolaki, Downes, Speier, Elias, & Pouratian, ). Our results are in line with these studies, and suggest that tractography based guidance during tcMRgFUS treatment strategy could be very beneficial.…”

The dentato-rubro-thalamic tract as the potential common deep brain stimulation target for tremor of various origin: an observational case series

“…Moreover, it was hypothesized that the mentioned target regions (Vim, STR, cZI) are actually confluent with the DRT which is hit in different (thalamic and subthalamic) parts ("three stereotactic targets, one fiber pathway" concept) [13,14]. Several groups have since used DTI tractography to modulate the DRT in DBS surgery [3,19,21,57,60] and have meticulously refined targeting strategies with good results [43]. Moreover, evidence for DRT as being a marker structure for the identification of the Vim at MCP level has been reported on stimulation grounds [14,57] and based on related intraoperative electrophysiology [29].…”

A Comprehensive Review of Brain Connectomics and Imaging to Improve Deep Brain Stimulation Outcomes

“…Akram and colleagues found, in a small series of ET and PD patients, that greater VTA overlap with the DRTC was present in patients with better tremor control . In contradiction, Nowacki and colleagues was unable to reproduce the findings of greater tremor improvement with DRTC stimulation using four different tractography methods . As opposed to the previously discussed ET studies, which used patient‐specific data, Al Fatly and colleagues found similar connectivity associated with VTAs in the posterior subthalamic area, and these VTAs correlated with greater improvement in tremor when using normative connectome data …”

“…Other studies have highlighted the tremor suppression associated with stimulation of the DRTC—a fiber tract that connects the dentate nucleus with the red nucleus, thalamus, and PMC . Akram and colleagues found, in a small series of ET and PD patients, that greater VTA overlap with the DRTC was present in patients with better tremor control .…”