• Lina Raffaella Barzaghi, Luigi Albano, Claudia Scudieri, Carmen Rosaria Gigliotti, Francesco Nadin, Del Vecchio Antonella A Department of Medical Physics, IRCCS San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy., and Pietro Mortini.
• Department of Neurosurgery and Gamma Knife Radiosurgery, IRCCS San Raffaele Scientific Institute and Vita-Salute University, Milan, Italy. Electronic address: barzaghi.linaraffaella@hsr.it.
• World Neurosurg. 2020 Oct 1; 142: e140-e150.

ObjectiveGamma Knife radiosurgery (GKRS) is a well-defined treatment for trigeminal neuralgia. The aim of this study was to determine how the GKRS planning might change on the basis of the patient's own anatomy and how to best choose the target location.MethodsTrigeminal cisternal length, pontotrigeminal angle, and distance between middle of the shot and emergence were evaluated in 112 consecutive GKRS plans for trigeminal neuralgia. Correlations with pain outcomes and facial hypoesthesia were analyzed.ResultsThe mean angle was 29° ± 4.4° and 37° ± 0.9°, respectively, in patients developing and not developing severe hypoesthesia (P = 0.045), despite no significant difference on brainstem dose (11.9 ± 0.8 and 10.5 ± 0.3 Gy; P = 0.22). The length of the nerve was not relevant on clinical outcomes but the shot-emergence distance (mean 8.1 ± 0.2 mm) depended on both trigeminal length and angle (P = 0.01). At constant prescription dose, 6-month cumulative rates of pain relief and control without therapy were 52.9% when the shot-emergence distance was ≤8 mm, whereas 25% when this distance was >8 mm (P = 0.017). The maintenance of good pain control was more long lasting in the first group (49.5 ± 6.6 vs. 25.4 ± 5 months; P = 0.006) with a 5-year cumulative rate of 70% and 26%, respectively (P < 0.001).ConclusionsThe pontotrigeminal angle and the shot-emergence distance should be considered during GKRS planning: the first as a potential risk factor for hypoesthesia, and the second should not exceed 8 mm.Copyright © 2020 Elsevier Inc. All rights reserved.

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