MATERIAL and METHODS: A retrospective study was conducted.The study involved 171 patients with severe facial pain caused by TN. Pain intensity was measured using a pre/post-BNI scale. Group A (85 patients) received 90 Gy using a single isocenter at REZ with a 4mm collimator, while Group B (86 patients) received 90 Gy at two isocenters of the REZ and distal cisternal segment. Statistical analyses were done to assess differences between post-BNI scores and pain-free durations in the groups.

RESULTS: Both groups had a mean patient age of 50 years. Group A had a longer presurgical pain duration (98 months) than Group B (78 months). In Group A, 33% reported pain relief to BNI class II and 67% to class III, while in Group B, 70% reported pain relief to BNI class I and 30% to BNI class II. Group A had a 40% 8-week pain relief rate, while Group B had a higher percentage of painfree durations of 6-7 weeks (21%) and 9 weeks (39%). Group B had a higher incidence of post-op facial numbness (27% vs. 14% in Group A). Significant differences existed between post-BNI pain intensities and pain-free durations in both groups.

CONCLUSION: Patients who received 90 Gy radiation at two isocenters had better outcomes than those with a single isocenter for GKRS. While Group B experienced earlier pain relief, Group A had fewer side effects. Two-isocenter GKRS is a safe and effective alternative for TN patients with a better pain management profile but an increased risk of facial hypoesthesia. Keywords : Gamma knife radiosurgery, Trigeminal neuralgia, Isocenter, Root entry zone, Barrow Neurological Institute pain scale