Gamma knife radiosurgery for trigeminal neuralgia: comparing the use of a 4-mm versus concentric 4- and 8-mm collimators

Stereotact Funct Neurosurg. 2004;82(1):49-57. doi: 10.1159/000076661.


Purpose: Gamma knife (GK) radiosurgery for trigeminal neuralgia (TN) has been effective in 50-80% of cases when using a single 4-mm collimator and a maximum dose of 60-90 Gy. Attempting to improve the response rate by increasing the dose may lead to increased risk of facial numbness or disturbed sensation. Combined use of 4- and 8-mm collimators results in a larger target volume, which would potentially treat a larger region of the nerve without increasing the maximum dose.

Materials and methods: One hundred-one patients suffering from medically refractory TN were evaluated. Fifty-four were treated with a single shot using a 4-mm helmet and 47 with concentrically aimed, equally weighted 4- and 8-mm helmets. 75 Gy were prescribed to the 100% isodose line (using a 4-mm helmet output factor of 0.80) in all cases. The outcome was assessed by interview or outpatient visit.

Results: An excellent/good response was seen in 57.8 vs. 71.4%, respectively, with a partial response of 13.3 vs. 2.3%, respectively (p > 0.05). Pain recurrence occurred in 28.6 vs. 23.2%, respectively (p > 0.05).

Conclusion: The use of a combined concentric 4- and 8-mm collimator treatment for medically refractory TN at a maximum dose of 75 Gy does not improve outcome as compared with a single 4-mm collimator with an equivalent maximum dose.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Chi-Square Distribution
  • Female
  • Follow-Up Studies
  • Gamma Rays / therapeutic use*
  • Humans
  • Male
  • Middle Aged
  • Radiosurgery / instrumentation*
  • Radiosurgery / methods*
  • Statistics, Nonparametric
  • Trigeminal Neuralgia / physiopathology
  • Trigeminal Neuralgia / surgery*