title: Predictive nomogram for the durability of pain relief from gamma knife radiation surgery in the treatment of trigeminal neuralgia.
abstract: OBJECTIVE
  To determine factors associated with the durability of stereotactic radiation surgery (SRS) for treatment of trigeminal neuralgia (TN).
  
  
  METHODS
  Between 1999 and 2008, 446 of 777 patients with TN underwent SRS and had evaluable follow-up in our electronic medical records and phone interview records. The median follow-up was 21.2 months. The Barrow Neurologic Institute (BNI) pain scale was used to determine pre- and post-SRS pain. Dose-volume anatomical measurements, Burchiel pain subtype, pain quality, prior procedures, and medication usage were included in this retrospective cohort to identify factors impacting the time to BNI 4-5 pain relapse by using Cox proportional hazard regression. An internet-based nomogram was constructed based on predictive factors of durable relief pre- and posttreatment at 6-month intervals.
  
  
  RESULTS
  Rates of freedom from BNI 4-5 failure at 1, 3, and 5 years were 84.5%, 70.4%, and 46.9%, respectively. Pain relief was BNI 1-3 at 1, 3, and 5 years in 86.1%, 74.3%, and 51.3% of type 1 patients; 79.3%, 46.2%, and 29.3% of type 2 patients; and 62.7%, 50.2%, and 25% of atypical facial pain patients. BNI type 1 pain score was achieved at 1, 3, and 5 years in 62.9%, 43.5%, and 22.0% of patients with type 1 pain and in 47.5%, 25.2%, and 9.2% of type 2 patients, respectively. Only 13% of patients with atypical facial pain achieved BNI 1 response; 42% of patients developed post-Gamma Knife radiation surgery (GKRS) trigeminal dysfunction. Multivariate analysis revealed that post-SRS numbness (hazard ratio [HR], 0.47; P<.0001), type 1 (vs type 2) TN (HR, 0.6; P=.02), and improved post-SRS BNI score at 6 months (HR, 0.009; P<.0001) were predictive of a durable pain response.
  
  
  CONCLUSIONS
  The durability of SRS for TN depends on the presenting Burchiel pain type, the post-SRS BNI score, and the presence of post-SRS facial numbness. The durability of pain relief can be estimated pre- and posttreatment by using our nomogram for situations when the potential of relapse may guide the decision for initial intervention.
authors.affiliation: Department of Radiation Oncology, Wake Forest Baptist Medical Center, Winston-Salem, North Carolina. Electronic address: johnthomas75@gmail.com.
authors.forename: John T
authors.initials: JT
authors.lastname: Lucas
authors.affiliation: Biomedical Informatics Center, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Nida
authors.affiliation: Department of Biostatistical Sciences, Section of Biostatistics, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Scott
authors.initials: S
authors.lastname: Isom
authors.affiliation: Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Kopriva
authors.initials: K
authors.lastname: Marshall
authors.affiliation: Department of Radiation Oncology, Wake Forest Baptist Medical Center, Winston-Salem, North Carolina.
authors.forename: John D
authors.initials: JD
authors.lastname: Bourland
authors.affiliation: Department of Neurosurgery, Wake Forest Baptist Medical Center, Winston-Salem, North Carolina.
authors.forename: Adrian W
authors.initials: AW
authors.lastname: Laxton
authors.affiliation: Department of Neurosurgery, Wake Forest Baptist Medical Center, Winston-Salem, North Carolina.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Tatter
authors.affiliation: Department of Radiation Oncology, Wake Forest Baptist Medical Center, Winston-Salem, North Carolina.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Chan
mesh_terms: D000368:Aged; D005157:Facial Pain / Q000209:etiology / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049451:Nomograms; D059408:Pain Management / Q000379:methods*; D010147:Pain Measurement / Q000379:methods*; D010149:Postoperative Pain / Q000628:therapy; D016016:Proportional Hazards Models; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D012008:Recurrence; D012189:Retrospective Studies; D013997:Time Factors; D014277:Trigeminal Neuralgia / Q000601:surgery*