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


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).


CONCLUSIONS
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.
Department of Neurosurgery, The Cleveland Clinic Health System Gamma Knife Center, Cleveland, Ohio, USA.
Andrew A
AA
Kanner
Gennady
G
Neyman
John H
JH
Suh
Martin S
MS
Weinhous
Shih-Yuan
SY
Lee
Gene H
GH
Barnett
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D005260:Female; D005500:Follow-Up Studies; D005720:Gamma Rays / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods*; D018709:Statistics, Nonparametric; D014277:Trigeminal Neuralgia / Q000503:physiopathology / Q000601:surgery*