Repeated Gamma Knife surgery for refractory trigeminal neuralgia

Object. Repeated Gamma Knife surgery (GKS) for trigeminal neuralgia (TN) is an acceptable method for refractory cases but not well established in terms of dose effect and nerve tolerance. The authors report their experience in 28 patients over 3.5 years of follow up. Methods. Between 1999 and 2004, a total of 28 patients with recurrent or residual TN underwent repeated GKS. The median follow-up periods were 52 and 43 months after the first and repeated procedures, respectively. The entry zone of the trigeminal nerve was targeted using a 4-mm collimator and treated with 40 to 76 Gy as maximal dose. Additive doses ranged between I 10 and 152 Gy. The median duration of symptoms was 4.86 years. There were 12 women (46%) and 16 men (54%). At the last evaluation, a total of 19 patients (68%) reported pain relief. Of these patients, 13 were no longer taking pain medications. Significant recurrent or residual pain was noted in nine patients after a median follow up of 12 months (range 6-48 months). New onset of facial numbness was noted in 10 patients. An additive dose above 115 Gy was found to be associated with facial numbness and nonfacial numbness (p = 0.047). No definite additive dose correlation with pain relief was noted (p = 0.23). Conclusions. Repeated GKS established durable pain relief in a majority of patients, and a higher additive dose (> 115 Gy) tended to cause facial numbness. However, a prospective trial is needed to fully assess the efficacy and late complications of GKS.