3526 - Neurostructural Paradox in Trigeminal Neuralgia: VBM Reveals Pain Network Remodeling after Radiosurgery
Presenter(s)
V. Shankar1, V. R. Anand2, D. Arjundas3, S. Cholayil1, G. Laksmipathy4, V. L. Arulselvan5, S. Muthukani6, S. Ghosh7, V. Sai Shreya8, and C. Haritha9; 1Apollo Cancer Centers, Chennai, India, 2Sai Neuro Hospital, Chennai, India, 3Chief Neurologist, Mercury Hospital, Chennai, India, 4Dept. of Neurology, Apollo Hospitals, Greams Unit, Chennai, India, 5Dept.of Neurology, Apollo Hospitals, Greams Unit, Chennai, India, 6Dept. of Neurology, Apollo Hospitals, Greams Road, Chennai, India, 7Dept. of Neurosurgery, Apollo Proton Cancer Center, Chennai, India, 8ACSR Govt. Medical College, Nellore, India, 9C.R.Reddy Cancer Center, Nellore, India
Purpose/Objective(s): Trigeminal neuralgia (TN) radiosurgery effectively alleviates pain but may induce complex structural changes in both pain-processing networks and irradiated brainstem regions. This study investigates the longitudinal evolution of gray matter volume (GMV) following radiosurgery, hypothesizing bidirectional GMV trajectories: recovery in supratentorial pain-modulatory regions due to pain relief and decline in irradiated pontine areas due to delayed radiation effects.
Materials/Methods: Twelve refractory typical TN patients (mean age 54.2 ± 7.8 years; 6 female) underwent a frameless robotic radiosurgery (85Gy, DREZ target) with longitudinal 3T MRI at baseline, 6mo, 12mo, and 2 yr. Twelve age- and sex-matched healthy controls provided normative GMV data. Voxel-based morphometry (VBM) analyzed GMV changes in pain-processing regions (anterior cingulate cortex [ACC], insula, thalamus) and irradiated pontine areas. Clinical outcomes, including pain relief BNI scale and sensory complications (hypoesthesia), were correlated with GMV dynamics. Repeated-measures ANOVA and paired t-tests assessed within-group GMV changes, while independent t-tests compared TN patients with controls. Pearson correlation (r) evaluated relationships between GMV dynamics, pain relief (BNI scale), and hypoesthesia severity. A p-value <0.05 was considered statistically significant.
Results: In the irradiated pontine region, GMV initially increased at 6mo (+4.1%, p = 0.03), suggesting acute edema, followed by significant decline at 12mo (-6.5%, p = 0.01) and 2y (-8.2%, p = 0.005). In supratentorial regions, ACC and insula GMV stabilized by 6mo (+0.8%, p = 0.21) after pre-treatment declines, with partial recovery at 12mo (+3.2%, p = 0.04). By 2y, patients with sustained pain relief (BNI I-II, n=9) exhibited near-normal ACC/insula GMV (-2.1% vs. controls, p = 0.12), while refractory cases (n=3) showed progressive thalamic GMV loss (-8.3%, p = 0.02). Pontine GMV reductions correlated with hypoesthesia severity (r = -0.69, p = 0.01), whereas ACC recovery correlated with pain-free duration (r = 0.62, p = 0.03).
Conclusion: Post-radiosurgery GMV follows divergent pathways: transient edema and progressive decline in irradiated brainstem regions contrast with recovery in supratentorial pain networks, contingent on treatment success. Sustained ACC/insula normalization may reflect adaptive neuroplasticity linked to pain remission, while pontine GMV loss underscores radiation toxicity risks. These dual trajectories highlight radiosurgery’s nuanced impact, advocating for refined dosimetry to maximize pain relief while minimizing brainstem impact. Current study, being the first reported in literature, has Limitations of small cohort from single-center; multi-center studies with larger samples are needed to validate GMV biomarkers for outcome prediction and therapeutic optimization.