We evaluated the prognostic radiation parameters for pain relief outcomes and complications after Gamma Knife radiosurgery for trigeminal neuralgia.Higher integrated dose lend to a higher rate of trigeminal dysfunction without significantly increased pain relief rate (p=0.006).As the pain relief rate and trigeminal nerve dysfunction related to multi-factor,the integrated dose of trigeminal nerve root may give us useful information to better understand the radiobiological effect on clinical outcome following GKR for TN.Purpose The radiobiological effect of Gamma Knife treatment for trigeminal neuralgia is still remained to further investigate.This retrospective study is to analyze the influence of different radiation parameters to the outcome of the treatment.treatment for trigeminal neuralgia.Methods and Materials Seventy-three patients with refractory trigeminal neuralgia treated by a maximum dose of 75-90 Gy using either one (n=41) or two (n=32) isocenters were intensively followed up.Using the GammaPlan system,the integrated dose delivered to the trigeminal nerve root within the prepontine cistern and the nerve root volume were calculated for each patient,.Pain relief were quantified based on the Barrow Neurological Institute Scale for TN.Relationship between the clinical outcome and the radiation parameters were statistically analyzed.Results At the last follow-up,21 patients (28.8%),22 patients(30.1%),19 patients(26%),6 patients(8.2%) and 5 patients(6.8%) had GRADE Ⅰ-Ⅴ pain outcome respectively.And the average mean dose delivered to the trigeminal nerve root,average integrated dose(mJ)and nerve root volume in prepontine cistern were 45.29 Gy,4,26 mJ and 98.47 mm3 respectively.The pain relief rate were not significantly improved by a higher amount of integrated dose received by the trigeminal nerve root in prepontine cistern.However,incidence of trigeminal nerve toxicity might be increased(p=0.006).Conclusions Our limited results suggested that a higher integrated dose may increase incidence of trigeminal nerve toxicity with no significant benefits in short-term pain relief when the maximal dose be within 75-90 Gy.However,more randomized controlled studies with large number of cases should be carried out to verify the best treatment strategy of GKR for TN.