3527 - Phased Relief: Optimizing Dose for Bilateral Trigeminal Neuralgia Radiosurgery
Presenter(s)
V. Shankar1, D. Arjundas2, S. Ghosh3, G. Laksmipathy4, S. Meenakshi Sundaram5, S. Cholayil1, V. L. Arulselvan6, S. Muthukani7, V. R. Anand8, K. Bhanu9, and V. Sai Shreya10; 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, 5Apollo Hospitals, Madurai, India, 6Dept.of Neurology, Apollo Hospitals, Greams Unit, Chennai, India, 7Dept. of Neurology, Apollo Hospitals, Greams Road, Chennai, India, 8Sai Neuro Hospital, Chennai, India, 9Mehtas Hospital,, Chennai, India, 10ACSR Govt. Medical College, Nellore, India
Purpose/Objective(s): Bilateral trigeminal neuralgia (BTN), a rare condition that poses a unique therapeutic challenge as aggressive interventions risk bilateral complications which impair QOL like facial numbness and corneal anesthesia, This study aims to evaluate the efficacy and safety of staged radiosurgery (SRS) for BTN, with a focus on adaptive dosing strategies to balance pain control and toxicity reduction.
Materials/Methods: A retrospective cohort analysis (between 2010-2023) was conducted on 12 patients with medically refractory BTN treated using a frameless robotic radiosurgery. Patients were stratified into two cohorts: idiopathic TN (n=7) and MS-associated TN (n=5). Treatment was delivered in two stages, separated by a minimum 6-month interval to allow toxicity assessment from the first procedure. The initial SRS targeted the trigeminal nerve root entry zone (REZ) at a median dose of 85 Gy (range: 80–90 Gy) prescribed to the 50% isodose line. For the second-side treatment, doses were adapted based on post-first-SRS toxicity: patients with minimal facial numbness (BNI grade =III) received 80 Gy (n=4), while those with significant numbness (BNI grade IV) received reduced doses of 70–75 Gy (n=8). Outcomes were assessed using BNI pain intensity scale and facial numbness scale. Toxicity included bothersome numbness (BNI IV) or severe complications (e.g., anesthesia dolorosa). Non-parametric statistical analyses were employed due to small sample size, with significance set at p<0.05.
Results: Initial pain relief (BNI I–IIIb) was achieved in 71.4% (10/14) after the first RS and 57.1% (8/14) after the second. At 2 years, 57.1% (8/14) maintained adequate control (BNI I–IIIa). Recurrence occurred in 42.9% (6/14), with a median time to recurrence of 14 months (first-treated side) and 18 months (second-treated side). Patients with MS had lower success rates (40% vs. 66.7% in idiopathic TN; p=0.29) and earlier recurrence (median: 11 vs. 16 months). Facial numbness (BNI IV) developed in 21.4% (3/14) after the first RS and 28.6% (4/14) after the second; one patient (7.1%) experienced bilateral mild numbness. No severe complications (e.g., anesthesia dolorosa, motor deficits) occurred. Higher radiation doses (=80 Gy) correlated with better pain control (p=0.04) but increased numbness risk (p=0.07).
Conclusion: Staged radiosurgery, with a minimum time interval of 6mo, provides effective pain relief for BTN, with careful dose adaptation playing a critical role in mitigating bilateral toxicity. Reducing the second-side dose to 70–75 Gy in patients with first-side numbness significantly lowers the risk of facial sensory complications without compromising pain control. Patients with MS exhibit lower response rates, necessitating further investigation into alternative strategies. These findings highlight the importance of individualized dosing to optimize therapeutic outcomes in BTN, though larger studies are needed to refine dosing and timing protocols.