Dose Rate Impact On The Outcome Of Patients With Trigeminal Neuralgia After Gamma Knife Surgery

Ionut Gobej1, Adyl Melhaoui1, Michael Park1, Denis Porcheron1, Jean Regis2

1Hospital Timone, Marseille, France. 2

Keywords: trigeminal neuralgia, outcome, dosimetry, pain, radiosurgery

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       The impact of the dose rate on the radiobiological effect of Gamma Knife Surgery (GKS) is still a matter of debate.
     In order to avoid the influence of multiisocentrism, target volume we have addressed this issue in the group of patient undergoing GKS for trigeminal neuralgia.
     The clinical outcome of the 40 patients treated before and 40 after GK reloading (June 2006) in Timone University Hospital have been reviewed comparatively.
     The precise date of the reloading was June 12th, 2006. The average dose at the max was 85 Gy (80-90). The shot was placed at the retrogasserian target 7-8 mm anteriorly to the V nerve emergence from the brainstem. Patients were followed prospectively with clinical evaluation at 3,6 and 12 months.
     The dose rate was 1,289 Gy/mn for the group one (before reloading) and 3,744 Gy/mn for the group two (after reloading). The rate of complete pain cessation was 31/40 and 37/40 after a mean delay of 26 and 15 days respectively in the group 1 and 2 (p=0,06). The rate of hypoesthesia (p=0,17) was 6 discrete in group 1 and 6 discrete and 3 severe in group 2 (none were disabling). The number of paresthesia (P=0,09) was 5 discrete in group 1, 7 discrete and 2 severe in group 2.
     This is a retrospective study.
     There is a trend for faster effect, high rate of complete pain cessation and higher rate of recurrence and slightly higher rate of toxicity in patients treated with a higher dose rate.
      None of these differences is reaching statistical significance.


Project Roles:

I. Gobej (), A. Melhaoui (), M. Park (), D. Porcheron (), J. Regis ()