title: Predictive variables for the successful treatment of trigeminal neuralgia with gamma knife radiosurgery.
abstract: BACKGROUND
  Gamma Knife radiosurgery (GKRS) has been reported to be an effective modality to treat trigeminal neuralgia.
  
  
  OBJECTIVE
  To determine predictive factors for the successful treatment of trigeminal neuralgia with GKRS.
  
  
  METHODS
  Between 1999 and 2008, 777 GKRS procedures for patients with trigeminal neuralgia were performed at our institution. Evaluable follow-up data were obtained for 448 patients. Median follow-up time was 20.9 months (range, 3-86 months). The mean maximum prescribed dose was 88 Gy (range, 80-97 Gy). Dosimetric variables recorded included dorsal root entry zone dose, pons maximum dose, dose to the petrous dural ridge, and cisternal nerve length.
  
  
  RESULTS
  By 3 months after GKRS, 86% of patients achieved Barrow Neurologic Institute I to III pain scores, with 43% of patients achieving a Barrow Neurologic Institute I pain score. Twenty-six percent of patients reported posttreatment facial numbness; 28% of patients reported a post-GKRS procedure for relapsed pain, and median time to next procedure was 4.4 years. Multivariate analysis revealed that the development of postsurgical numbness (odds ratio [OR], 2.76; P = .006) was the dominant factor predictive of efficacy. Longer cisternal nerve length (OR, 0.85; P = .005), prior radiofrequency ablation (OR, 0.35; P = .028), and diabetes mellitus (OR, 0.38; P = .013) predicted decreased efficacy. The mean dose delivered to the dorsal root entry zone dose in patients who developed facial numbness (57.6 Gy) was more than the mean dose (47.3 Gy) given to patients who did not develop numbness (P = .02).
  
  
  CONCLUSIONS
  The development of post-GKRS facial numbness is a dominant factor that predicts for efficacy of GKRS. History of diabetes mellitus or previous radiofrequency ablation may portend worsened outcome.
authors.affiliation: Department of Radiation Oncology, Wake Forest University Health Sciences, Winston-Salem, North Carolina, USA.
authors.forename: Kopriva
authors.initials: K
authors.lastname: Marshall
authors.forename: Michael D
authors.initials: MD
authors.lastname: Chan
authors.forename: Thomas P
authors.initials: TP
authors.lastname: McCoy
authors.forename: Adam C
authors.initials: AC
authors.lastname: Aubuchon
authors.forename: J Daniel
authors.initials: JD
authors.lastname: Bourland
authors.forename: Kevin P
authors.initials: KP
authors.lastname: McMullen
authors.forename: Allan F
authors.initials: AF
authors.lastname: deGuzman
authors.forename: Michael T
authors.initials: MT
authors.lastname: Munley
authors.forename: Edward G
authors.initials: EG
authors.lastname: Shaw
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Tatter
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Ellis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011183:Postoperative Complications / Q000453:epidemiology*; D011237:Predictive Value of Tests; D011829:Radiation Dosage; D016634:Radiosurgery / Q000009:adverse effects* / Q000706:statistics & numerical data*; D012307:Risk Factors; D016896:Treatment Outcome; D014277:Trigeminal Neuralgia / Q000453:epidemiology* / Q000601:surgery*; D055815:Young Adult