Pujol Sonia, Cabeen Ryan P, Yelnik Jérôme, François Chantal, Fernandez Vidal Sara, Karachi Carine, Bardinet Eric, Cosgrove G Rees, Kikinis Ron
Surgical Planning Laboratory, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States.
Laboratory of Neuro Imaging, Stevens Institute for Neuroimaging and Informatics, Keck School of Medicine of the USC, University of Southern California, Los Angeles, CA, United States.
Front Neurol. 2022 Apr 25;13:791092. doi: 10.3389/fneur.2022.791092. eCollection 2022.
The subthalamic nucleus (STN) is an effective neurosurgical target to improve motor symptoms in Parkinson's Disease (PD) patients. MR-guided Focused Ultrasound (MRgFUS) subthalamotomy is being explored as a therapeutic alternative to Deep Brain Stimulation (DBS) of the STN. The hyperdirect pathway provides a direct connection between the cortex and the STN and is likely to play a key role in the therapeutic effects of MRgFUS intervention in PD patients.
This study aims to investigate the topography and somatotopy of hyperdirect pathway projections from the primary motor cortex (M1).
We used advanced multi-fiber tractography and high-resolution diffusion MRI data acquired on five subjects of the Human Connectome Project (HCP) to reconstruct hyperdirect pathway projections from M1. Two neuroanatomy experts reviewed the anatomical accuracy of the tracts. We extracted the fascicles arising from the trunk, arm, hand, face and tongue area from the reconstructed pathways. We assessed the variability among subjects based on the fractional anisotropy (FA) and mean diffusivity (MD) of the fibers. We evaluated the spatial arrangement of the different fascicles using the Dice Similarity Coefficient (DSC) of spatial overlap and the centroids of the bundles.
We successfully reconstructed hyperdirect pathway projections from M1 in all five subjects. The tracts were in agreement with the expected anatomy. We identified hyperdirect pathway fascicles projecting from the trunk, arm, hand, face and tongue area in all subjects. Tract-derived measurements showed low variability among subjects, and similar distributions of FA and MD values among the fascicles projecting from different M1 areas. We found an anterolateral somatotopic arrangement of the fascicles in the corona radiata, and an average overlap of 0.63 in the internal capsule and 0.65 in the zona incerta.
Multi-fiber tractography combined with high-resolution diffusion MRI data enables the identification of the somatotopic organization of the hyperdirect pathway. Our preliminary results suggest that the subdivisions of the hyperdirect pathway projecting from the trunk, arm, hand, face, and tongue motor area are intermixed at the level of the zona incerta and posterior limb of the internal capsule, with a predominantly overlapping topographical organization in both regions. Subject-specific knowledge of the hyperdirect pathway somatotopy could help optimize target definition in MRgFUS intervention.
丘脑底核（STN）是改善帕金森病（PD）患者运动症状的有效神经外科靶点。磁共振引导聚焦超声（MRgFUS）丘脑底核切开术正在被探索作为STN深部脑刺激（DBS）的一种治疗替代方法。超直接通路在皮层和STN之间提供了直接连接，并且可能在MRgFUS干预PD患者的治疗效果中起关键作用。
本研究旨在调查来自初级运动皮层（M1）的超直接通路投射的拓扑结构和躯体定位。
我们使用从人类连接组计划（HCP）的五名受试者获取的先进多纤维束成像和高分辨率扩散磁共振成像数据，重建来自M1区域超直接通路的投射。两名神经解剖学专家审查了纤维束的解剖学准确性。我们从重建的通路中提取源自躯干、手臂、手部、面部和舌部区域的纤维束。我们基于纤维的分数各向异性（FA）和平均扩散率（MD）评估受试者之间的变异性。我们使用空间重叠的骰子相似系数（DSC）和纤维束的质心评估不同纤维束的空间排列。
我们在所有五名受试者中成功重建了来自M1的超直接通路投射。纤维束与预期的解剖结构一致。我们在所有受试者中识别出从躯干、手臂、手部、面部和舌部区域投射的超直接通路纤维束。纤维束衍生的测量结果显示受试者之间变异性较低，并且在从不同M1区域投射的纤维束之间FA和MD值的分布相似。我们在放射冠中发现纤维束呈前外侧躯体定位排列，在内囊中的平均重叠率为0.63，在未定带中的平均重叠率为0.65。
多纤维束成像结合高分辨率扩散磁共振成像数据能够识别超直接通路的躯体定位组织。我们的初步结果表明，从躯干、手臂、手部、面部和舌部运动区域投射的超直接通路分支在内囊后肢和未定带水平相互交织，在这两个区域中主要是重叠的拓扑结构。超直接通路躯体定位的个体特异性知识有助于优化MRgFUS干预中的靶点定义。
