2432 - Feasibility and Safety of Multiple Courses of Gamma Knife Radiosurgery Treatment to Recurrent Trigeminal Neuralgia: A Single-Institutional Clinical Outcomes

J. N. Trosper¹, D. Fabian², W. St Clair³, T. Pittman⁴, and D. Pokhrel¹; ¹University of Kentucky, Department of Radiation Medicine, Lexington, KY, ²University of Kentucky, Lexington, KY, ³University of Kentucky, Radiation Medicine, Lexington, KY, ⁴University of Kentucky, Department of Neurosurgery, Lexington, KY

Purpose/Objective(s): Leksell Perfexion Gamma Knife Radiosurgery (GKRS) has been utilized to provide a treatment alternative for treatment resistant Trigeminal Neuralgia (TN) patients with a refractory or contraindication to surgery. If a minimally invasive, same day frame based GKRS can effectively provide pain relief, then multiple retreatments via highly precise GKRS unit can be a patient’s best alternative to polypharmacy. We analyzed the effectiveness, complication rate, and time intervals between GKRS retreatments at our historic GKRS center. Materials/

Methods: This study focuses on the cohort of patients with a history of multiple treatment episodes spanning from 2009 to 2023. A comprehensive examination of patient records, encompassing notes, and imaging reports was conducted. A single 4 mm shot was used; first treatment was at prepontine cistern area. To avoid the shot overlap, subsequent retreatment shot(s) were placed at the posterior aspect of Meckel’s cave (anterior to previous shot) while respecting the temporal lobe (maximum dose < 21 Gy) and brainstem (maximum <18 Gy). The initial prescription was 45 Gy to 50% isodose line (IDL) with a maximum dose of 90 Gy at the middle of the trigeminal nerve. Re-treatment dosage ranged between 30–40 Gy to 50% IDL (maximum, 60–80 Gy). Outcomes were assessed with the Barrow Neurological Institute (BNI) pain scoring system (Class I–V). Retreatments were considered ineffective if BNI class did not improve after retreatment or if symptoms recurred, requiring additional intervention within 6 months post-retreatment of TN.
Results: Thirty-one patients were identified that received two or more courses of GKRS. Average patient age was 65.8 years (yrs) (range, 37-89 yrs) at the first treatment. Twenty of the 31 patients (65%) had atypical TN, including all 3 patients that received three or more GKRS treatments. One atypical patient received a total of five courses of GKRS over 11 yrs intervals without complications. Three (9.6%) atypical TN patients failed to GKRS retreatment. Of these 1 underwent surgery within 6 months due to pain and 2 others failed to improve BNI scoring, however they didn’t receive additional interventions. Average and median intervals between first and second treatment were 2.9 yrs and 1.4 yrs, respectively. Following the second course of GKRS, 3 patients experienced post-retreatment facial numbness, which was managed with medication. No patients demonstrated treatment-related intracranial toxicity.
Conclusion: Most patients (> 90%) undergoing multiple courses of GKRS experienced improved pain control based on a decreased BNI score with none of them experiencing radiation induced toxicity concerns. This suggests that multiple courses of GKRS, with adequate recovery time and shot placement strategy, are a safe and effective treatment option for recurrent or refractory patients of TN including atypical cases. Further dedicated prospective studies are needed to validate the potential of repeat dose escalation up to initial dose of 90 Gy.