Gamma knife surgery for trigeminal neuralgia: improved initial response with two isocenters and increasing dose

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Object. The authors sought to evaluate the initial response of trigeminal neuralgia (TN) to gamma knife surgery (GKS) based on the number of shots delivered and radiation dose.

Methods. Between September 1998 and September 2003, some 63 patients with TN refractory to medical or surgical management underwent GKS at Upstate Medical University. Ten patients had multiple sclerosis and 25 patients had undergone prior invasive treatment. Gamma knife surgery was delivered to the trigeminal nerve root entry zone in one shot in 27 patients or two shots in 36 patients. The radiation dose was escalated to less than or equal to 80 Gy in 20 patients, 85 Gy in 21 patients, and greater than or equal to 90 Gy in 22 patients. Pain before and after GKS was assessed using the Barrow Neurological Institute Pain Scale and the improvement score was analyzed as a function of dose grouping and number of shots.

Sixty patients were available for evaluation, with an initial overall and complete response rate of 90% and 27%, respectively. There was a greater improvement score for patients who were treated with two shots compared with one shot, mean 2.83 compared with 1.72 (p < 0.001). There was an increased improvement in score at each dose escalation level: less than or equal to 80 Gy (p = 0.017), 85 Gy (p < 0.001), and greater than or equal to 90 Gy (p < 0.001). Linear regression analysis also indicated that there was a greater response with an increased dose (p = 0.021). Patients treated with two shots were more likely to receive a higher dose (p < 0.001). There were no severe complications. Five patients developed mild facial numbness.

Conclusions. Gamma knife surgery is an effective therapy for TN. Initial response rates appear to correlate with the number of shots and dose.

Article Information

Address reprint requests to: Chung T. Chung, M.D., Department of Radiation Oncology, Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210. email: chungc@upstate.edu.

© AANS, except where prohibited by US copyright law.

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Figures

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    Graph showing the distribution of GKS dose escalation from 70 to 95 Gy for the study population.

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    Gamma knife surgery plans for one-shot compared with two-shot treatment showing the 10-Gy (outer) and 50% isodose lines (inner) and dose—volume histograms of the pons.

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    Graph showing the response to GKS according to dose grouping, which revealed a statistically significant improvement in the mean BNI score at each dose escalation level.

  • View in gallery

    Scatter plot of dose compared with improvement score on linear regression analysis (p = 0.021).

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