Gamma Knife radiosurgery for type 1 idiopathic trigeminal neuralgia

Alberto Franzin1, Davide Milani2, Piero Picozzi, MD3, G Dib4, Nicola Boari2, Antonella Del Vecchio5, Pietro Mortini2

1Mi, Italy 2Dept. of Neurosurgery and Radiosurgery IRCCS S. Raffaele, Università Vita-Salut 3Department of Neurosurgery, IRCCS San Raffaele 4Dept. of Neurology, Università degli Studi di Brescia, Brescia, Italy 5Milan, Italy

Keywords: pain, gamma knife, trigeminal neuralgia, radiosurgery, outcome

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     Trigeminal neuralgia radiosurgery has become common. Technical aspects of this procedure vary between centers.
     The aim of this study is to evaluate Gamma Knife radiosurgery (GK) efficacy in trigeminal neuralgia treatment in terms of pain relief, time needed to achieve pain relief, pain relief maintainance, and side effects, and clinical (age, symptoms duration, previous treatments) and radiosurgical (dose, shot placement, dose rate) variables influence to clinical outcome and side effects incidence.
     Between August 2001 and February 2010 100 patients (48 females, 52 males , mean age 65.4 years, range 38-79 years) were treated by GK for type 1 idiopathic trigeminal neuralgia.
      Leksell stereotactic frame was positioned in all patients under local anesthesia and mild sedation. T2* True FISP MRIs were taken. GammaPlan was used for treatment planning. A single 4 mm isocenter was placed along the intracisternal portion of trigeminal nerve: in 41 cases in the proximal part (mean distance from root entry zone 4.3 mm), and in 59 cases in the distal part (mean distance from root entry zone 8.1 mm). Mean maximal dose was 76 Gy (range 70-90 Gy). Patient were re-evaluated every 3-6 months after treatment and at the end of follow-up. Mean follow-up was 47 months (range 12-111 months). Pre and post treatment Barrow Neurological Institute (BNI) score was adopted to assess semi quantitatively pain intensity. Side effects impact on quality of life was evaluated with Barrow Neurological Institute facial numbness score. Descriptive and inferential statistical analysis assessed response to treatment, time needed to achieve the maximum pain relief, maintenance of pain relief, side effects and the possible predictive role on outcome and side effects incidence of some clinical and radiosurgical variables.
     A good outcome (BNI I- IIIb) was achieved in 71% and 70% of patients, at 3 and 12 months after GK respectively. 74% of responders achieved pain relienf in less then a month, 19% in 6 months, 7% in 12 months. Just 2 patients suffered side effects reducing the quality of life. The actuarial rate of achieving and maintaining a good outcome (BNI I-IIIb) was 70%, 63%, 57%, 55% at 1, 2, 5 and 10 years after GK respectively. In this series neither short and long term outcome nor side effect incidence were influenced by clinical (age, symptom duration, previous treatments) or radiosurgical (proximal or distal target, maximal dose, brainstem radiation exposure, dose rate) variables.
     This was a retrospective study.
     The results obtained in this quite large series of patients with a long follow-up, confirm the safety and efficacy of GK as a therapeutic option for trigeminal neuralgia.
     Refinements in dose planning and patient selection may improve outcomes.


Project Roles:

A. Franzin (), D. Milani (), P. Picozzi (), G. Dib (), N. Boari (), A. Del Vecchio (), P. Mortini ()