title: Do carbamazepine, gabapentin, or other anticonvulsants exert sufficient radioprotective effects to alter responses from trigeminal neuralgia radiosurgery?
abstract: OBJECTIVE
  Laboratory studies have documented radioprotective effects with carbamazepine. We sought to determine whether carbamazepine or other anticonvulsant/neuroleptic drugs would show significant radioprotective effects in patients undergoing high-dose small-volume radiosurgery for trigeminal neuralgia.
  
  
  METHODS
  We conducted a retrospective review of 200 patients undergoing Gamma Knife (Elekta Instrument AB, Stockholm, Sweden) stereotactic radiosurgery for trigeminal neuralgia between February 1995 and May 2008. We selected patients treated with a maximum dose of 80 Gy with 4-mm diameter collimators, with no previous microvascular decompression, and follow-up ≥6 months (median, 24 months; range, 6-153 months). At the time of radiosurgery, 28 patients were taking no anticonvulsants, 62 only carbamazepine, 35 only gabapentin, 21 carbamazepine plus gabapentin, 17 carbamazepine plus other anticonvulsants, and 9 gabapentin plus other anticonvulsants, and 28 were taking other anticonvulsants or combinations.
  
  
  RESULTS
  Pain improvement developed post-radiosurgery in 187 of 200 patients (93.5%). Initial complete pain relief developed in 84 of 200 patients (42%). Post-radiosurgery trigeminal neuropathy developed in 27 of 200 patients (13.5%). We could not significantly correlate pain improvement or initial complete pain relief with use of carbamazepine, gabapentin, or use of any anticonvulsants/neuroleptic drugs or other factors in univariate or multivariate analysis. Post-radiosurgery numbness/paresthesias correlated with the use of gabapentin (1 of 36 patients with gabapentin vs. 7 of 28 without, p = 0.017). In multivariate analysis, decreasing age, purely typical pain, and use of gabapentin correlated (p = 0.008, p = 0.005, and p = 0.021) with lower risks of developing post-radiosurgery trigeminal neuropathy. New post-radiosurgery numbness/paresthesias developed in 3% (1 of 36), 5% (4 of 81), and 13% (23 of 187) of patients on gabapentin alone, with age ≤70 years, and Type 1 typical trigeminal neuralgia pain compared with 25% (7 of 28), 20% (23 of 114), and 33% (4 of 12) of patients taking no anticonvulsants, age >70 years, and partly atypical Type 2 trigeminal neuralgia, respectively.
  
  
  CONCLUSIONS
  The use of carbamazepine or gabapentin at the time of radiosurgery does not decrease the rates of obtaining partial or complete pain relief after radiosurgery, but gabapentin may reduce the risks of developing post-radiosurgery trigeminal neuropathy.
authors.affiliation: Department of Radiation Oncology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA. flickingerjc@upmc.edu
authors.forename: John C
authors.initials: JC
authors.lastname: Flickinger
authors.forename: Hyun
authors.initials: H
authors.lastname: Kim
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Kano
authors.forename: Joel S
authors.initials: JS
authors.lastname: Greenberger
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Arai
authors.forename: Ajay
authors.initials: A
authors.lastname: Niranjan
authors.forename: L Dade
authors.initials: LD
authors.lastname: Lunsford
authors.forename: Douglas
authors.initials: D
authors.lastname: Kondziolka
authors.forename: John C
authors.initials: JC
authors.lastname: Flickinger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000588:Amines / Q000494:pharmacology*; D000704:Analysis of Variance; D000927:Anticonvulsants / Q000494:pharmacology*; D002220:Carbamazepine / Q000494:pharmacology*; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology*; D005260:Female; D000077206:Gabapentin; D006801:Humans; D008297:Male; D008875:Middle Aged; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D014277:Trigeminal Neuralgia / Q000209:etiology / Q000601:surgery*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D000588:Amines; D000927:Anticonvulsants; D003509:Cyclohexanecarboxylic Acids; D011837:Radiation-Protective Agents; D002220:Carbamazepine; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin