Efficacy and Safety of Microvascular Decompression in Patients with Trigeminal Neuralgia Previously Treated with Gamma Knife Stereotactic Radiosurgery.

Background/Objectives: Gamma Knife stereotactic radiosurgery (GKS) controls classical trigeminal neuralgia (TN) in 70-90% of patients, but pain recurs in a substantial minority, and these patients are then considered for microvascular decompression (MVD). Whether radiation-induced arachnoid thickening, vessel-nerve adhesion and nerve atrophy compromise the safety or efficacy of subsequent MVD remains unresolved, and the available series are small. The objective of this study was to determine whether prior GKS alters the efficacy or the safety of subsequent MVD. Methods: We performed a retrospective, two-center cohort study of consecutive patients with classical TN who underwent MVD between 2015 and 2025. Of more than 1571 patients treated with GKS for TN during this period, 35 subsequently underwent MVD for insufficient pain relief (GKS+); they were compared with 60 consecutive patients who underwent primary MVD without prior radiosurgery (GKS-). The primary outcome was pain control on the Barrow Neurological Institute (BNI) scale at last follow-up, dichotomized as good (BNI I-III) or poor (BNI IV-V). Secondary outcomes were postoperative adverse events, medication-free status, intraoperative findings, intradural operative time and length of stay. Results: Good long-term pain control was achieved in 31 of 35 GKS+ patients (88.6%) and 55 of 60 GKS- patients (91.7%; p = 0.725) over a mean follow-up of 31.2 and 39.7 months, respectively. Radiation-related intraoperative changes-most often arachnoid thickening (62.9%)-were present in all GKS+ patients. Composite adverse events occurred in 31.4% of GKS+ and 36.7% of GKS- patients (p = 0.660), but the majority were trigeminal sensory disturbances (22.9% and 25.0%, respectively); non-sensory complications occurred in 3 GKS+ patients (8.6%) and 7 GKS- patients (11.7%; p = 0.741). At long-term follow-up, 48.6% of GKS+ and 60.0% of GKS- patients were medication-free (p = 0.294). There were no major neurological deficits and no surgery-related deaths in either cohort. Conclusions: Prior Gamma Knife radiosurgery did not reduce the efficacy or the safety of subsequent microvascular decompression, despite consistently more demanding intraoperative conditions. MVD remains an appropriate rescue option for persistent or recurrent trigeminal neuralgia after failed radiosurgery.