Objective: This study aimed to determine the affected side in trigeminal neuralgia by examining the digitized angle ratio value between the bilateral trigeminal nerve root axis and the pontine tangent line. Methods: Trigeminal nerve-related MRI from 81 patients with trigeminal neuralgia (TNG) and 20 healthy persons were divided into normal and diseased groups. All the patient's films were scanned to form the images stored in compute. The following skull base MRI parameters were measured by Image J software: 1. bilateral trigeminal nerve root-pontine tangent line angle (T-P angle) values were measured. 2. Clinical symptoms were used to record the affected side of diseased patients, and 3. Nerve vascular confliction (NVC) and the side with NVC were subdivided (none/left/right/both sides). The normal T-test proved that P Value between the normal group and the diseased group. The T-P angle Ratio of the normal group was utilized to estimate the normal patient Ratio to establish the 95% confidence interval (CI). In diseased group, if the ratio was >= the reference value, the afflicted side was determined by comparing the max T-P angle with the actual affected side for accuracy. A binomial distribution test verified its statistical significance. Results: The T-P angle was significantly different between patients with TNG and normal subjects (p < 0.001). The T-P angle ratio (R) >= 1.238 was used to diagnose the affected side, achieving an overall accuracy rate of 82% (95% CI: 75%-89%). For patients without NVC, the accuracy was 78% (95% CI: 60%-95%), while for those with unilateral NVC, it was 91% (95% CI: 82%-100%), and for those with bilateral NVC, it was 69% (95% CI: 52%- 86%). For 1 <= R < 1.238, the accuracy for diagnosing the affected side using NVC was 80% (95% CI: 67%-93%). Conclusion: The T-P angle is significantly higher in TNG patients than in normal patients (p < 0.001)., making it a valuable diagnostic tool. This measurement aids in guiding microvascular decompression surgery, particularly in non-vascular compression cases, and enhances postoperative evaluation. Future integration into standard protocols could improve surgical outcomes and patient care.