Radiosurgical decompression of trigeminal nerve and its correlation with functional outcome in tumor related trigeminal neuralgia

Background The target selection during gammaknife radiosurgery(GKRS) in cases of tumor related trigeminal neuralgia(TRTGN) is always debatable. Here we discuss the correlation of regression of tumor size, degree of release of the nerve with long term pain control. Methods Total 50 cases of TRTGN were treated with GKRS (tumor was targeted) during the period March 2012 and March 2023. Post GKRS radiology was categorised in to three types(Type 1 – tumor volume remained same/reduced, additional segment of nerve not seen, Type 2 – tumor volume reduced, additional segment of trigeminal nerve seen but tumor still adherent to the nerve, Type 3 – tumor volume reduced, adjacent nerve seen completely separated from tumor). Pre and post GKRS pain score(BNI I to III –good, BNI IV&V – poor) was correlated with the above subgroups. Result At a median follow up of 46.5 months 18 cases have type 1, 23 showed type 2 and 9 showed type 3 radiological response. Ten(55.5%) patients with type 1, 15(65.21%) with type 2 and 7(77.8%) with type 3 responses had good pain control. The outcome among these three was not statistically significant(p=0.519).Five patients with type 3 radiological response were off medication which was statistically better than type 1 radiological response with three patients(p = 0.012) and type2 radiological response with two patients(p = 0.002). Conclusion Post GKRS tumor volume reduction may show good pain control in TRTGN. This further allows visualization of additional segment of nerve that can be targeted in the second session for treating recurrent or failed cases.