3530 - White Matter Fingerprints: Tract-Specific DTI Predictors for Radiosurgical Thalamotomy in Parkinson's Tremor

02:30pm - 03:45pm PT

Hall F

Screen: 23

POSTER

Presenter(s)

Vangipuram Shankar, MD, MBBS - Apollo Proton Cancer Centre, Chennai , Tamil Nadu

V. Shankar¹, D. Arjundas², S. Ghosh³, S. Cholayil¹, G. Laksmipathy⁴, J. Verghese⁵, K. Bhanu⁶, V. L. Arulselvan⁷, H. Sarkar⁸, and A. V. Ramana Murthy⁹; ¹Apollo Cancer Centers, Chennai, India, ²Chief Neurologist, Mercury Hospital, Chennai, India, ³Dept. of Neurosurgery, Apollo Proton Cancer Center, Chennai, India, ⁴Dept. of Neurology, Apollo Hospitals, Greams Unit, Chennai, India, ⁵Dept.of Neurosurgery, Apollo Hospitals, Greams unit, Chennai, India, ⁶Mehtas Hospital,, Chennai, India, ⁷Dept.of Neurology, Apollo Hospitals, Greams Unit, Chennai, India, ⁸Dept.of Neurosurgery, Apollo Hospitals, Greams Unit, Chennai, India, ⁹Apollo Speciality Hospital, Nellore, India

Purpose/Objective(s): Diffusion Tensor Imaging (DTI) evaluates white matter integrity in motor circuits, which are disrupted in Parkinson’s disease (PD) tremor. This study investigates whether preoperative DTI metrics of the ventral intermediate nucleus (Vim) thalamus and adjacent tracts predict tremor suppression after radiosurgical thalamotomy.

Materials/Methods: 12 patients with unilateral, medication-refractory PD tremor (mean age 65.3 ± 7.1 years) underwent 3T MRI with DTI preoperatively followed by a frameless robotic radiosurgery(110gy VIM thalamotomy). Inclusion criteria: UPDRS-TS =8, Pre-operative tremor response to levodopa, idiopathic PD (DaT-SPECT-confirmed), Intact Cognition. Exclusion Criteria: Patients with atypical parkinsonism, bradykinesia/rigidity, prior brain surgery, or MRI contraindications. Tractography was performed to assess fractional anisotropy (FA) and mean diffusivity (MD) within the (1) dentato-rubro-thalamic (DRT) tract - primary pathway linking cerebellum, red nucleus, thalamus (2) thalamocortical (CTT) pathways which are essential for sensorimotor integration & (3) basal ganglia-thalamic projections which are involved in tremor modulation. Tremor severity was evaluated preoperatively and postoperatively using UPDRS & FTM-TRS. The primary endpoint was percentage tremor reduction at a median follow-up of 24 months. Statistical analyses included Spearman’s correlation (DTI metrics vs. tremor improvement), Mann-Whitney U test (FA-based group comparison), multivariate regression (predictors of response), and ROC analysis (FA threshold, AUC, sensitivity, specificity).

Results:

Higher preoperative FA in the Vim (p = 0.002) and CTT (p = 0.023) correlated with greater tremor reduction.
Patients with FA >0.35 in the Vim (n = 8) achieved 85% improvement vs. 52% in those with FA =0.35 (p = 0.006).
Multivariate regression identified Vim FA as the strongest predictor (p = 0.002), explaining 68% of outcome variance (R² = 0.68).
ROC analysis demonstrated high predictive accuracy for Vim FA (AUC = 0.87, 95% CI: 0.71–1.01) with 87.7% sensitivity and 75.5% specificity at the optimal threshold (FA = 0.35).
No adverse events occurred.

Conclusion: Preoperative DTI tractography, particularly Vim FA, is a robust biomarker for predicting thalamotomy outcomes in PD tremor. The strong correlation between Vim FA and tremor suppression highlights the critical role of structural connectivity in tremor pathophysiology and treatment response. These findings support integrating DTI into preoperative planning to refine treatment efficacy. Future studies combining DTI with resting-state fMRI may enhance personalized neurosurgical strategies for movement disorders.