Gamma Knife Radiosurgery For Trigeminal Neuralgia: Influence Of The Irradiation Dose To The Long-term Outcome Of 114 Patients

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

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     The optimal irradiation dose and target of gamma knife radiosurgery (GKR) for trigeminal neuralgia (TN) remains controversial.
     We analyzed the effects and trigeminal nerve deficits of GKR using fused MR images and two isocenters.
     From January 2005 to March 2009, 114 patients underwent GKR at our center. The patients were divided into two groups: group I of high dose (86-90Gy) and group II of low dose (80-85Gy). All patients were followed up by periodical phone call or personal interview.
     MR images of turbo spin echo and constructive interference in steady state sequences were fused for treatment plan. The maximum central dose of 80-90Gy was delivered to the trigeminal nerve root with two isocenters via a 4-mm collimator helmet. And the plug pattern was used to limit the dose to the pons to be under 20Gy. The pain remission was classified to complete (100% pain control), partial and no effect (no ease of pain severity). The effects and the trigeminal nerve deficits were compared between the two groups.
      Mean follow-up was 29.6 months (6-58 months). There were 71 patients in group I and 43 in group II. The patients of complete,partial pain remission and no effect were 54(76%), 14(19.7%), 3(4.2%) in group I and 31(72.1%), 10(23.2%), 2(4.7%) in group II. The average time before complete remission was 3.2 weeks of group I which was statistically shorter than 4.3 weeks of group II. Recurrence occurred in 3 patients of group I and 6 patients of group II 21-53 months after the treatments. 31 patients of group I and 18 patients of group II experienced tolerable facial numbness. Temporalis muscle spasm occurred in one patient of group I during 2-6 weeks after the treatment and was self-relieved. No other complications occurred. The differences of the effects and facial numbness between two groups were not significant.
     This is a retrospective study.
     The results supported the safety and efficacy of GKR with two isocenters for TN.
     A higher irradiation dose may result in shorter remission time and lower recurrence without increase the incidence of facial numbness.


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