Validation of Tenths Stereotactic Coordinates Method Using Probabilistic Tractography of the Ansa Lenticularis in Parkinson's disease Patients.

ABSTRACT

OBJECTIVE: To evaluate the accuracy of stereotactic coordinates to target the Ansa Lenticularis (AL) using two surgical planning methods, the conventional millimeter method (MM) and the normalized Tenths Method (TM), assessed through individualized probabilistic tractography. METHODS: Stereotactic targeting of the AL was assessed in two groups 16 patients with Parkinson's disease (PD) and 16 healthy controls from Group 1, and 39 PD patients from Group 2. Structural and diffusion MRI probabilistic tractography identified the AL based on the Schaltenbrand-Wahren Atlas. The MM defined stereotactic coordinates in millimeters, while the TM refined the planning by dividing the intercommissural line (AC-PC) distance into 10 equal parts, normalizing the "X," "Y," and "Z" coordinates for each patient. We subsequently compared the percentage of structural connectivity (%conn) of the AL with predefined regions of interest (ROIs), including the frontopontine-corticothalamic tracts (Fp-Ct), Globus Pallidus Internus-Ventral Oral Anterior (GPi-Voa), and Ventral Oral Posterior (GPi-Vop), and quantified the streamlines in 142 brain hemispheres using the MM and TM coordinates. RESULTS: Despite anatomical variations in intercommissural (AC-PC) line lengths between both groups (22.5±2.09 mm and 24.4±2.56 mm, respectively; p=0.002), as well as differences in MRI acquisition parameters, we found that the TM significantly enhanced streamline identification and %conn compared to the MM. These enhancements were noted across ROIs Fp-Ct and GPi-Voa in both hemispheres, and GPi-Vop in the left (p<0.001) and right hemispheres (p=0.03). CONCLUSION: TM surpasses MM in identifying the structural connectivity between the AL and predefined ROIs, underscoring the advantages of coordinate normalization. However, variations in AC-PC line lengths and Euclidean distances between methods could lead to inaccuracies in the coordinate settings, potentially affecting the precision of structural connectivity and the efficacy of therapeutic outcomes.