Gamma Knife Radiosurgery For Trigeminal Neuralgia: A Comparison Of Dose Protocols

Warren Boling1, John C Frich1, André Kalend1, Bengt Karlsson2

1West Virginia University, Morgantown, USA 2Singapore, Singapore

Keywords: gamma knife, dose planning, trigeminal neuralgia, pain, outcome

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     Since the 1950’s when radiosurgery was first applied to the treatment of trigeminal neuralgia (TN), an extensive experience worldwide, with Gamma Knife Radiosurgery (GKR) in particular, has demonstrated its utility for medically intractable TN. However, an optimum prescription dose has not been determined. Literature suggests patients that receive at least 70Gy fare better (Kondziolka, et al, 1996).
     We studied whether higher doses provide further benefit.
     Sixty-Three patients were treated with GKR for TN since 2002. All had intractable typical TN except three with multiple sclerosis (all in 80Gy group) and these individuals were removed from the analysis. Two patients without follow-up (one in each treatment group) were excluded. Typical TN was treated with 80Gy in 26 patients, and 85Gy was delivered to 37 patients. Mean age was 71 years. Twenty-eight were women. Eighteen had a procedure for TN prior to GKR (13 in 80Gy group, P=.005).
     This retrospective analysis evaluated all patients treated with GKR since the program inception at West Virginia University. The early maximum dose was 80Gy. In 2005 the protocol was changed to 85Gy.This study compares the two doses for efficacy to control TN pain and side effects of treatment. A Kaplan-Meier statistic (K-M) analyzed the duration of pain freedom. Log Rank test compared K-M of the two dose groups. Chi squared test compared categorical data between the groups.
     Mean follow-up period after GKR in pain free patients was 37 months (range 6 to 72) treated with 80Gy and 22 months (range 6 to 52) treated with 85Gy. Three reported a new face sensory disturbance after 80Gy and 6 after 85Gy. Two were bothered by the numbness (one each in 80Gy and 85Gy groups). Fourteen in 80Gy group failed GKR with pain recurrence despite medication, whereas 8 failed GKR after 85Gy. K-M analysis showed at 29 months 50% patients failed after 80Gy, and 75% had continued pain relief after 85GY. This difference was significant (P=0.04).
     This was a retrospective study.
       In our patient population, 85Gy dose for TN provided a more robust pain relief with a similar rate of facial sensory changes.
     We think that 85 Gy is a good choice for trigeminal neuralgia dose selection.


Project Roles:

W. Boling (), J. Frich (), A. Kalend (), B. Karlsson ()