Tractography-based targeting of the thalamic ventral intermediate nucleus (T-VIM) is a novel method conferring patient-specific selection of VIM coordinates for tremor surgery; however, its accuracy and clinical utility in magnetic resonance imaging–guided focused ultrasound (MRgFUS) thalamotomy compared to conventional indirect targeting has not been specifically addressed. This retrospective study sought to compare the treatment locations and potential adverse effect profiles of T-VIM with indirect targeting in a large cohort of MRgFUS thalamotomy patients.
T-VIM was performed using diffusion tractography outlining the pyramidal and medial lemniscus tracts in 43 MRgFUS thalamotomy patients. T-VIM coordinates were compared with the indirect treatment coordinates used in the procedure. Thalamotomy lesions were delineated on postoperative T1-weighted images and displaced (“translated”) by the anteroposterior and mediolateral difference between T-VIM and treatment coordinates. Both translated and actual lesions were normalized to standard space and subsequently overlaid with areas previously reported to be associated with an increased risk of motor and sensory adverse effects when lesioned during MRgFUS thalamotomy.
T-VIM coordinates were 2.18 mm anterior and 1.82 mm medial to the “final” indirect treatment coordinates. Translated lesions lay more squarely within the boundaries of the VIM compared to nontranslated lesions and showed significantly less overlap with areas associated with sensory adverse effects. Translated lesions overlapped less with areas associated with motor adverse effects; however, this difference was not significant.
T-VIM leads to the selection of more anterior and medial coordinates than the conventional indirect methods. Lesions moved toward these anteromedial coordinates avoid areas associated with an increased risk of motor and sensory adverse effects, suggesting that T-VIM may improve clinical outcomes.
ABBREVIATIONSAC-PC = anterior commissure–posterior commissure; AP = anteroposterior; DBS = deep brain stimulation; DWI = diffusion-weighted imaging; MER = microelectrode recording; M-L = mediolateral; ML = medial lemniscus; MRgFUS = magnetic resonance imaging–guided focused ultrasound; PT = pyramidal tract; ROI = region of interest; SHSC = Sunnybrook Health Science Centre; VIM = ventral intermediate nucleus; T-VIM = tractography-based targeting of the VIM; TWH = Toronto Western Hospital; Voa = ventro-oralis anterior nucleus; Vop = ventro-oralis posterior nucleus.
Correspondence Mojgan Hodaie: Toronto Western Hospital, Toronto, ON, Canada. firstname.lastname@example.org.INCLUDE WHEN CITING Published online September 27, 2019; DOI: 10.3171/2019.6.JNS19612.
M.R. and G.J.B.E. contributed equally to this study and share first authorship.
Disclosures Dr. Fasano is a consultant for AbbVie, Medtronic, Boston Scientific, Sunovion, Chiesi Farmaceutici, UCB, and Ipsen; sits on the advisory boards of AbbVie, Boston Scientific, and Ipsen; and has received honoraria from AbbVie, Medtronic, Boston Scientific, Sunovion, Chiesi Farmaceutici, UCB, and Ipsen and grant funding from the University of Toronto, the Weston Foundation, AbbVie, Medtronic, and Boston Scientific. Dr. Devenyi is a consultant for MIAC AG. Dr. Hynynen holds patents with and receives royalties from Brigham and Women’s Hospital. Dr. Lozano is a consultant for Medtronic, St. Jude, Insightec, and Boston Scientific.Imaging data used in this paper include data from a cohort of patients who have been part of a study funded by Insightec. Dr. Hodaie or other research members have not had any industry support for this study, nor was there any specific funding for this imaging research.
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