Radiosurgery for classical trigeminal neuralgia: impact of shot size on clinical outcome

Abstract

Abstract Background This study compares the outcome of radiosurgery using two different shot sizes (5-mm and 6-mm) in patients suffering from medically refractory classical trigeminal neuralgia (TN). Methods All patients included in this open, prospective, non-controlled study were treated in a single institution for TN (95 patients) by LINAC single-dose radiosurgery using 5-mm shot (43 patients) or 6-mm shot (52 patients). The target was positioned on the intracisternal part of the trigeminal nerve. Results Mean Dmax (D0.035) to the brainstem that was higher in the 6-mm group: 12.6 Gy vs 21.3 Gy (p < 0.001). Pain control was significantly better in the 6-mm group: rates of pain-free patients at 12 and 24 months were respectively 90.2% and 87.8% vs. 73.6% and 73.6% in the 5-mm group (p = 0.045). Post-radiosurgical hypesthesia was more frequent in the 6-mm group: 47.0% and 58% vs.11.3% and 30.8% at 12 and 24 months (p = 0.002). To investigate the respective effect of shot size and dose to the brainstem on outcome, patients were separated in 3 groups: group 1 = 5-mm shot, (all Dmax < 25 Gy, 43 patients), group 2 = 6-mm shot, Dmax < 25 Gy (32 patients), group 3 = 6-mm shot Dmax > 25 Gy (20 patients). Rate of 12 months hypesthesia was 11.3%, 33.5% and 76.0%, respectively, p < 0.001 in each group. Rate of 12 months pain recurrence was 26.4%, 16.5% and 5% respectively (p = 0.11). Conclusion LINAC treatment with 6-mm shot achieved excellent pain control, but increased the rate of trigeminal nerve dysfunction, especially when the maximum dose to the brainstem was higher than 25 Gy.