Early Pain Relief Following Gamma Knife Radiosurgery for Trigeminal Neuralgia: Impact of Biologically Effective Dose
Abstract
Purpose
Evaluate our radiosurgical experience with trigeminal neuralgia treatment, with emphasis on short‑term pain relief and the influence of biologically effective dose (BED).
Methods
We retrospectively reviewed consecutive patients with trigeminal neuralgia treated at a single institution between 2020 – 2023. Gamma Knife Radiosurgery (GKRS) was delivered targeting the dorsal root entry zone with a prescribed dose of 85 Gy. The planning technique involved a 4mm shot without any sector blocking. The BED was calculated using A9 formalism. Treatment duration ranged from 33.39 to 64.42 minutes. Outcomes were evaluated using the Barrow Neurological Institute (BNI) pain intensity scale before and at 3 month follow up after the GK treatment. Additional data collected included the presence or absence of facial numbness post-treatment. Spearman’ rank coefficient was calculated to determine the relationship between the BED and improvements in BNI score (Pre-GK BNI – Post-GK BNI) as well as facial numbness.
Results
A total of 44 patients (65%female) underwent GKRS. The mean follow-up was 48 weeks, with a median follow-up of 14 weeks. BED ranged from 1945.5 to 2282.9 Gy. At 3 months follow-up, 37 of 44 patients (84%) demonstrated improvement in the BNI scale. No improvement was reported in 7 patients. Overall, 12 patients achieved complete pain relief (BNI I or II) and 22 patients achieved adequate pain relief (BNI III). A weak correlation (Spearman’s rank ρ=0.1) was observed between higher BED and improvement in BNI score. The average maximum dose to the brainstem was 47.2±4.8 Gy. Any facial numbness following treatment was observed in 21/44(48%) cases. No correlation (Spearman’s rank ρ=0.009) was found between the BED and facial numbness.
Conclusion
GKRS demonstrated effective early pain relief for trigeminal neuralgia, with BED evaluation indicating a potential relationship with BNI pain outcomes. Further research into optimizing BED parameters could improve treatment effectiveness.