Gamma knife treatment of trigeminal neuralgia

Effectiveness and limitations of Gamma Knife treatment for various kinds of trigeminal neuralgia (typical, atypical and mixed types) were analyzed from the data of 54 cases treated over the past 4 years. The mean patient age was 74 years (range 50 to 101 years). Forty five patients with typical trigeminal neuralgia, four patients with atypical facial pain and five patients with mixed type trigeminal neuralgia were evaluated. Isodose distribution determined with a 4 mm collimator was centered on the root entry zone of the trigeminal nerve in 35 cases and centered on the retro-Gasserian trigeminal nerve in 19 cases. The maximum dose range used was 70 to 80 Gy. Median follow-up after radiosurgery was 21.4 months (range 3 to 54 months). Typical trigeminal neuralgia treated at the root entry zone became pain free without medication in 53.6% (15/28), 78.6% (22/28) and 78.6% (22/28) of the patients after 3, 6 and 12 months, respectively, while, that treated at the retro-Gasserian nerve became pain free in 29.4% (5/17), 53.8% (7/13) and 70.0% (7/10) of the patients after 3, 6 and 8 months. No matter whether the target was the root entry zone or the retro-Gasserian nerve, 70 to 78% of patients became pain free without medication when examined at 8 to 12 months after radiosurgery. Facial hypesthesia including localized slight hypesthesia occurred in 13 to 20% of the patients at 12 to 24 months after radiosurgery, but no patients developed any other new neurological deficits or systemic complications. Patients with atypical trigeminal neuralgia did not respond well to this treatment. Further study is required to determine the optimal target and dose. Because of its noninvasive nature, radiosurgery is an attractive option for treatment of typical and mixed typed trigeminal pain, particularly in elderly patients and patients not amenable to the various surgical methods available for treatment of trigeminal neuralgia. (author)