Factors affecting outcome in non-isocentic stereotactic radiosurgery for trigeminal neuralgia in a large cohort of patients
EANS Academy. Conti A. 09/25/19; 275684; EP07015
Assoc. Prof. Alfredo Conti
Assoc. Prof. Alfredo Conti

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Objective: stereotactic radiosurgery (SRS) is an effective modality for treatment of trigeminal neuralgia (TN). Nevertheless, a proportion of patients will experience recurrence and about 20% may report sensory disturbances. To evaluate predictors of efficacy and safety of image-guided robotic radiosurgery, we determined the impact of trigeminal nerve volume and the nerve dose/volume relationship, together with relevant clinical characteristics.
Methods: 295 patients underwent nonisocentric CyberKnife radiosurgery between 2008 and 2018 in 2 italian and 1 german CyberKnife centers. In 33 cases the treatment was repeated a second time. In 17 patients the TN was secondary to multiple sclerosis (MS). Trigeminal pain was classified according to the Barrow Neurological Institute (BNI) pain scale and the numerical rating scale (NRS). The sensory disturbances were graded according the BNI hypoesthesia scale.
Results: Median follow-up was 40.8 mo; median dose 75 Gy; median target volume 40 mm3 ; median prescription dose 60 Gy (80% isodose line). Actuarial pain control rate (BNI class I-III) at 6, 12, 24, 36, 48, 60 mo were 93.5%, 85.8%, 79.7%, 72%, 68%, 61% respectively. Overall, 22.6% developed sensory disturbances. One patient (0.4%) developed BNI grade IV dysfunction; 18 (7%) developed BNI grade III (somewhat bothersome) hypoesthesia after retreatment; BNI grade II (not bothersome) hypoesthesia was reported by 45 patients (15.2%) after retreatment.
Smaller nerve volume (< 30 vs.> 30 mm3), lower prescription dose (< 58 vs. >58 Gy), and lower integral dose (< 1 Gy) were associated with treatment failure (P= .01, P= .02, P= .03, respectively). Re-irradiation and high integral dose (>1.6 Gy) predicted sensory disturbance (P < .001 and < 0.05 respectively).
Conclusions: The ratio of dose to nerve volume may predict recurrence of TN pain and sensory disturbances after nonisocentric SRS. Interestingly, the integral dose may differ significantly in treatments using apparently similar dose and volume constraints.
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