(P041) Clinical Outcomes of Gamma Knife Stereotactic Radiosurgery (GK-SRS) for Painful Trigeminal Neuropathy (TNP) 

David Zaenger, MD, M.N. Woodall, MD, Bryan M. Rabatic, PhD, MD, John R. Vender, MD, Waleed F. Mourad, MD, PhD, Joseph Kaminski, MD; Georgia Regents University

PURPOSE: Painful trigeminal neuropathy (PTN) is a rare variant of trigeminal neuralgia (TN) that necessitates prior trigeminal nerve injury, in addition to facial pain. While the evidence supporting the safety and efficacy of Gamma Knife stereotactic radiosurgery (GK-SRS) for medically refractory TN is well established, there is a limited body of literature concerning SRS for medically refractory PTN. We report our long-term clinical outcomes using GK-SRS for medically refractory PTN.

METHODS: This is a single-institution retrospective study of 320 patients treated with GK-SRS for TN between 2000 and 2013. From this cohort, 20 XRT-naive patients with PTN were identified. All patients failed initial treatment with medications, and seven (35%) received other invasive treatment (eg, microvascular decompression, rhizotomy) prior to SRS. All patients underwent frame-based single-fraction GK-SRS. Mean age was 61 years (range: 38–80 yr), and 75% of patients were female. Fifteen patients (80%) were Caucasian, four (15%) were African American, and one (5%) was Asian. Mean dose was 80 Gy (range: 80–90 Gy) to the 100% isodose line in a single fraction to the root entry zone of the involved trigeminal nerve (2–3 mm from the anterolateral surface of the pons). Complete response (CR), near-CR, and partial response (PR) were defined as being pain-free without medication, being pain-free with medication, and having reduced pain with medication, respectively.

RESULTS: With a median follow-up of 20 months (range: 3–70 mo), the overall response was 60%. Specifically, CR, near-CR, and PR rates were 27%, 20%, and 13%, respectively. No response (NR) was seen in 40% of patients, who had persistent, unchanged pain. For the 60% of patients who responded to GK-SRS, the mean time latency from SRS to response was 1 month (range: 0–2 mo). The pattern of pretreatment pain in the responders group was described as being dull rather than sharp compared with nonresponders. Additionally, when compared with the NR group, the CR group was significantly less likely to be exacerbated by daily activities pretreatment (0/4 [0%] vs 5/6 [83%]). No GK-SRS-induced grade ≥ 2 toxicities were reported.

CONCLUSIONS: SRS is both safe and efficacious for PTN. Additionally, prior to treatment, PTN patients who characterize their facial pain as dull and not exacerbated by daily activities are more likely to receive therapeutic benefit, with a mean response time of 1 month.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org