LAUSR

BACKGROUND Gamma Knife radiosurgery (GKRS) is a safe and effective treatment option for trigeminal neuralgia (TN). However, there is no objective, non-invasive, tool to identify non-responders or late responders to GKRS and to facilitate longitudinal patient management. We hypothesized that diffusivity metrics obtained three months after GKRS may correlate with response to treatment. METHODS Sixteen patients with TN treated with GKRS underwent pre-procedural and three-month post-procedural 3T brain MRI. Diffusion tensor metrics of axial diffusivity (AD), radial diffusivity (RD) and fractional anisotropy (FA) were extracted from the pontine segments, the root entry zones, and the distal cisternal segments of both trigeminal nerves. Diffusivity metrics at the three-month post-GKRS time point were compared with pain relief at last follow-up. Favorable response to GKRS was defined as pain intensity of Ⅰ-Ⅲ on the Barrow Neurological Institute scale. RESULTS The median clinical follow-up was 11 months (range 3- 18 months). Patients with favorable response to GKRS at last follow up had lower mean FA values at the pontine segment (p = 0.04) and increased mean RD values at the REZ (p = 0.032) of the treated trigeminal nerve on the 3 month DTI sequences as compared to the non-responders. CONCLUSION Diffusivity metrics changes on the treated trigeminal nerve at the three-month time point after GKRS for TN correlated with pain relief at last follow up. Further, well designed studies are warranted to establish the clinical application of DTI as a non-invasive, prognostic tool in patients with TN managed with GKRS.