Do carbamazepine, gabapentin, or other anticonvulsants exert sufficient radioprotective effects to alter responses to trigeminal neuralgia radiosurgery?John C. Flickinger, MD1, Hyun Kim2, Hideyuki Kano, MD, PhD3, Joel Greenberger2, Yoshio Arai2, Ajay Niranjan, MCh3, L. Dade Lunsford, MD3, Douglas Kondziolka, MSc, MD3, John Flickinger, Sr21Department of Radiation Oncology, University of Pittsburgh 2Dept. of Radiation Oncology, U. of Pittsburgh School of Medicine 3Department of Neurological Surgery, University of Pittsburgh Keywords: pain, gamma knife, trigeminal neuralgia, radiosurgery, anticonvulsant therapy
Laboratory studies have documented radioprotective effects with carbamazepine.
We sought to determine if carbamazepine or other
anticonvulsant/neuroleptic drugs showed significant radioprotective
effects in patients undergoing high-dose small-volume radiosurgery for
At the time of radiosurgery, 28 patients were taking no anticonvulsants,
62 only carbamazepine, 38 carbamazepine plus other anticonvulsants, 35
gabapentin alone, and 9 were taking other combinations.
We conducted a retrospective review of 200 patients undergoing Gamma Knife stereotactic radiosurgery for trigeminal neuralgia between 2/95-5/08. 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, range: 6-153).
Pain improvement developed post-radiosurgery in 187/200 (93.5%). Initial complete pain relief developed in 84/200 (42%). Post-radiosurgery trigeminal neuropathy developed in 27/200 (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 (1/36 vs. 7/28 without, p=0.017). In multivariate analysis, decreasing age, purely typical pain, and use of gabapentin correlated (p=0.008, 0.005, & 0.021) with lower risks of developing post-radiosurgery trigeminal neuropathy. New post-radiosurgery numbness/paresthesias developed in 3%(1/36), 5%(4/81) and 13%(23/187) of patients on gabapentin alone, with age<70, and type-1 typical trigeminal neuralgia pain compared to 25%(7/28), 20%(23/114), and 33%(4/12) of patients taking no anticonvulsants, age>70, and with partly atypical type-2 trigeminal neuralgia, respectively.
This was a retrospective study.
The use of carbamazepine or gabapentin at the time of radiosurgery does not decrease the rates of obtaining partial or complete pain relief with radiosurgery but gabapentin may reduce the risks of developing post-radiosurgery trigeminal neuropathy.
The findings of this study should be validated by other investigators. Project Roles:
J. Flickinger (), H. Kim (), H. Kano (), J. Greenberger (), Y. Arai (), A. Niranjan (), L. Lunsford (), D. Kondziolka (), J. Flickinger, Sr ()