Fiber Tractography-Guided MR-Guided Focused Ultrasound Pallidothalamic Tractotomy for Parkinson's Disease: A Case Report.

Pallidothalamic tractotomy (PTT) ablation using MR-guided focused ultrasound (MRgFUS) is a potential treatment option for medically refractory Parkinson's disease (PD). Because the PTT is surrounded by critical neural structures, precise stereotactic targeting is essential to minimize neurological adverse events. Diffusion tensor imaging (DTI) fiber tractography may improve targeting accuracy through direct visualization of the PTT. We report a single case of staged bilateral PTT ablation using MRgFUS in a 45-year-old woman with advanced PD. During the first procedure, DTI fiber tractography was used to visualize the PTT and determine the stereotactic target. During the second procedure, contralateral targeting was performed using mirrored anatomical coordinates derived from the initial tractography findings in order to maintain anatomical consistency. Motor symptoms improved substantially following both procedures. The Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III score improved from 24 to 11 after the first procedure and from 52 to 11 after the second procedure. No neurological adverse events were observed throughout the follow-up period. Although limited by the single-case design, this report suggests that DTI fiber tractography-guided targeting may improve the visualization and identification of the PTT during MRgFUS.