Diffusion MRI Tractography for Improved Transcranial MRI-guided Focused Ultrasound Thalamotomy Targeting for Essential Tremor

Figure. (a) The thalamocortical radiation (red) between the hand representation of Vim within the thalamus (blue) and motor cortex (green) can be robustly identified by diffusion tractography. (b) The tractography identified Vim (red-yellow) location overlaps with the lesioning location (green contour) selected by neurosurgeons in awake patients.

 

Essential tremor (ET) is one of the most common neurological diseases. Lesioning the ventral intermediate nucleus (Vim) of the thalamus using transcranial magnetic resonance imaging (MRI)-guided focused ultrasound (tcMRgFUS) is an effective and non-invasive approach to suppress the tremor. It is challenging, however, to locate the Vim, a small structure with low intrinsic contrast on standard structural MRI. The atlas based targeting method does not account for the anatomical variability between patients and lacks specificity to the hand representation within Vim, which is essential to suppress the hand tremor. Our study utilizes diffusion MRI tractography to locate the Vim by mapping the white matter pathways that conduct the electrical signals governing hand movement. On eight ET patients treated with tcMRgFUS at Stanford, it was found that higher overlap between the tractography-identified Vim location and the tcMRgFUS treatment-induced lesion location selected by neurosurgeons in awake patients highly correlated with better treatment outcome. Our study supports the use of diffusion tractography as a complementary approach to improve the current targeting methods for tcMRgFUS thalamotomy.

Tian Q, Wintermark M, Elias WJ, Ghanouni P, Halpern CH, Henderson JM, Huss DS, Goubran M, Thaler C, Airan R, Zeineh M, Pauly KB, McNab JA. Diffusion MRI Tractography for Improved Transcranial MRI-guided Focused Ultrasound Thalamotomy Targeting for Essential Tremor. NeuroImage: Clinical, 2018; 19: 572-580.

Link: https://www.sciencedirect.com/science/article/pii/S2213158218301566?via%3Dihub