1. Learn More At: www.DoctorVermeulen.com Dose-Response and Dose- Complications Relationships in Stereotactic Radiosurgery for Trigeminal Neuralgia Sandra Vermeulen MD, Robert Meier MD, Vivek Mehta MD, Ron Young MD, Francisco Li MS Northwest Gamma Knife Center, Seattle, WA, USA

2. Learn More At: www.DoctorVermeulen.com Trigeminal Neuralgia: Overview Definition: brief episodic, unilateral face pain, confined to one or more divisions of the 5 th nerve. Cause: tumors, vascular compression of the root entry zone, multiple sclerosis and idiopathic causes Pharmacotherapy is the initial treatment modality of choice Annual incidence in the United States: 15,000

3. Learn More At: www.DoctorVermeulen.com Purpose/Objective In Patients treated with Gamma Knife Radiosurgery for Trigeminal Neuralgia, to determine if a relationship exists between dose delivered, and the incidence of response, or the incidence of complications

4. Learn More At: www.DoctorVermeulen.com Material and Methods 382 patients with either typical or atypical TN were treated between August 1993 and January 2005 None had tumor or Multiple Sclerosis All were treated with a single 4-mm isocenter targeting the ipsilateral trigeminal nerve at the dorsal root entry zone Dose was prescribed at the Dmax

5. Learn More At: www.DoctorVermeulen.com Treatment Iso-Center

6. Learn More At: www.DoctorVermeulen.com Dose Protocols Three dose protocols were employed using an output factor or 0.87: 76 patients received 76 Gy 179 patients received 87 Gy 127 patients received 98 Gy

7. Learn More At: www.DoctorVermeulen.com Patient Characteristics Group Dose Group 1 76 Gy Group 2 87 Gy Group 3 98 Gy Patient No.76179127 Mean F/U4.16 yrs2.74 yrs3.76 yrs Sex (M/F)26/5068/11150/77 Mean Age63 yrs62 yrs60 yrs Location R/L48/2899/8061/66 Division No.>1: 48>1: 109>1:70 Pre-GK Procedures None/1/>1 41/16/19 None/1/>1 119/25/35 None/1/>1 89/17/21

8. Learn More At: www.DoctorVermeulen.com Treatment Characteristic Isodose20%30% 40%50% Group 1 76 Gy 11%1%63%25% Group 2 87 Gy 40%28%0%32% Group 3 98 Gy 63%0% 37%

9. Learn More At: www.DoctorVermeulen.com Results Treatment outcomes were measured at 6 months, at last follow-up and actuarially “Favorable” responders were patients rendered free of pain, either with or without medication Complications were defined as lasting neurologic deficits attributable to treatment and included numbness or paresthesias

10. Learn More At: www.DoctorVermeulen.com Pain Relief At 6 months post- treatment, “favorable” outcomes occurred with similar rates in all 3 groups Log-rank test showed no significant difference in the Kaplan-Meier curves for these three groups (p=0.835)

11. Learn More At: www.DoctorVermeulen.com Complications The only lasting complication was new numbness or paresthesia At 6 months, patients treated with higher doses more often developed sensory deficits (p<0.05)

12. Learn More At: www.DoctorVermeulen.com Severity of Numbness

13. Learn More At: www.DoctorVermeulen.com Conclusion In stereotactic radiosurgery for TN, escalation of maximum nerve dose from 76 Gy to 87 Gy to 98 Gy does not significantly improve pain relief, but is associated with a higher incidence of complications