title: Gamma knife radiosurgery for trigeminal neuralgia: results and potentially predictive parameters--part I: Idiopathic trigeminal neuralgia.
abstract: OBJECTIVE
  Gamma knife radiosurgery (GKR) is an increasingly used, minimally invasive treatment option for patients with trigeminal neuralgia (TN) refractory to medical therapy. This retrospective study evaluates the long-term results and side effects of GKR in the treatment of TN focusing on potentially predictive factors.
  
  
  METHODS
  One hundred sixty patients with TN were included in this study (minimum follow-up, >6 mo; mean, 37.4 mo; range, 6-144 mo). In 92 patients, GKR represented the first nonmedical option ("primary GKR"). In 68 patients, invasive treatments had been previously attempted. All patients were treated using a single 4-mm collimator shot targeting the pontine trigeminal root entry zone with a maximal dose of 75 to 95 Gy. Brainstem dose exposure never exceeded 15 Gy. Treatment outcome results were classified as Grade I (pain-free with no pharmacological treatment), Grade II (pain-free with pharmacological treatment), and Grade III (no result). Data were analyzed using the log-rank test for univariate analysis and the ordered logit model for multivariate analysis.
  
  
  RESULTS
  In the overall series, 98 (61%) out of 160 patients reached a Grade I outcome, 45 (29%) reached a Grade II outcome, and 17 (10%) patients had no results from GKR. These results were encouraging for patients with typical facial pain features and for patients treated by a "primary" gamma knife. Considering the global outcome, the most effective and safest dose was found to be in the 80 to 90 Gy range.
  
  
  CONCLUSIONS
  According to our experience, GKR represents a reliable second-line therapeutic approach for TN after pharmacological failure. Favorable prognostic factors include "primary GKR" and maximal GKR dose ranging between 80 and 90 Gy.
authors.affiliation: Department of Neurosurgery, University Hospital, Verona, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Longhi
authors.forename: Paolo
authors.initials: P
authors.lastname: Rizzo
authors.forename: Antonio
authors.initials: A
authors.lastname: Nicolato
authors.forename: Roberto
authors.initials: R
authors.lastname: Foroni
authors.forename: Mario
authors.initials: M
authors.lastname: Reggio
authors.forename: Massimo
authors.initials: M
authors.lastname: Gerosa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005069:Evaluation Studies as Topic; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D016896:Treatment Outcome; D014277:Trigeminal Neuralgia / Q000473:pathology / Q000601:surgery*