Salvage Gamma Knife radiosurgery for recurrent trigeminal neuralgia after microvascular decompression: clinical outcomes and imaging-guided targeting strategies

Objective This study aimed to evaluate the clinical outcomes of Gamma Knife radiosurgery (GKS) as a salvage treatment for patients with recurrent or residual trigeminal neuralgia (TN) following microvascular decompression (MVD), and to assess the utility of advanced magnetic resonance imaging techniques—particularly proton density-weighted imaging (PDWI)—for accurate target localization in post-surgical anatomy. Methods A prospective cohort of 17 patients with medically refractory TN who experienced recurrent or residual pain after MVD underwent GKS between May 2010 and May 2025. Imaging for treatment planning included T2-weighted, T1-weighted, contrast-enhanced T1-weighted, T2 VISTA (Volume ISotropic Turbo spin echo Acquisition; Philips Healthcare), and proton density-weighted sequences. Treatment was individualized using postoperative imaging findings rather than predefined anatomical targets. Outcomes were assessed using the Barrow Neurological Institute (BNI) pain scale. Results The mean interval between MVD and GKS was 48.1 months, with a mean post-GKS follow-up of 24.4 months. Good pain control (BNI grade I-IIIb) was achieved in 88.2% of patients. Most patients experienced significant pain relief within 6 months after treatment. The average maximal radiation dose was 85.9 Gy. Advanced imaging, especially PDWI, enabled better visualization of distorted or compressed trigeminal nerves and adjacent structures, facilitating accurate target selection despite anatomical changes due to prior surgery. Conclusion GKS is a safe and effective salvage treatment for TN after failed MVD, with a high rate of favorable pain control. Despite the challenges posed by postoperative anatomical distortion, individualized imaging-guided planning, particularly using PDWI, improves targeting accuracy and treatment efficacy.