LINAC Radiosurgery for Trigeminal Neuralgia

SSG25-06

LINAC Radiosurgery for Trigeminal Neuralgia

Scientific Papers

Presented on November 28, 2006
Presented as part of SSG25: ISP: Radiation Oncology and Radiobiology (Central Nervous System and Pediatric Malignancy)

Ashish K. Chawla MD, Presenter: Nothing to Disclose

Kaelyn Kappeler BS, Abstract Co-Author: Nothing to Disclose

Robert Siddon PhD, Abstract Co-Author: Nothing to Disclose

Timothy Eckel MD, Abstract Co-Author: Nothing to Disclose

Timothy Burke MD, Abstract Co-Author: Nothing to Disclose

Background: Trigeminal Neuralgia (TN) is a rare pain disorder that profoundly impacts quality of life. For patients with medication-refractory TN, stereotactic radiosurgery (SRS) directed at the affected nerve is a viable local treatment option. The majority of published SRS data deals with Gamma Knife technology. Linear accelerator (LINAC)-based SRS, with appropriate and reproducible isocenter stability, can also be utilized but data in this regard is limited.Our objective was to determine the results of LINAC radiosurgery in the management of medication-refractory TN at a single institution via retrospective review.

Between January 2004 and February 2006, 18 patients with idiopathic, medication-refractory unilateral TN were treated at our institution with SRS targeted to the trigeminal nerve root. About 2/3 of patients were female, and median age at treatment was 74 years. No patient had received previous SRS.Magnetic resonance imaging (MRI) was performed for localization of the trigeminal nerve and intra-procedural registration on a 1.5 Tesla imaging system. Axial acquired T1-weighted 3D spoiled gradient echo (SPGR) images were obtained after IV gadolinium, supplemented by multi-slab axially acquired 3D fast spin echo T2-weighted images to better localize the nerve in the para-pontine cistern. Utilizing Brainlab software, fusion was performed between this MRI and treatment-planning CT on the day of treatment.A frame-based SRS system (Brainlab Novalis) was utilized for immobilization, localization, and treatment delivery. A 4-mm collimator and 7-arc technique was employed to deliver a dose of 90 Gy in 1 fraction to the root of the trigeminal nerve. Isocenter location was modified such that the 50% isodose line abutted the brainstem surface. The Winston-Lutz test was performed prior to treatment delivery to ensure isocenter stability at approximately <0.5 mm.Pain response was recorded at initial follow-up (4 to 8 weeks following treatment), and serially at 3-month intervals via pain intensity score (0-10), frequency, and duration. Response categories included: none, minimal (< 50%), partial (> 50%), or complete (100%). Complications and pain medication intake status were tabulated at each visit.

Of 18 patients treated, 17 (94%) achieved a partial (> 50%) or greater initial response, at a median time of 4 weeks from SRS delivery. At a median follow-up of 12 months from treatment, 6/18 patients experienced pain persistence or recurrence (any increase above the lowest pain level achieved), for a crude recurrence rate of 33%. Utilizing Kaplan-Meier analysis, with persistence of pain scored as immediate failure, the actuarial rate of pain recurrence at 12 months was 28%. No complications were noted from radiotherapy delivery, but 17% of patients reported scalp pain at frame pin sites, which resolved within weeks in all cases. At the most recent follow-up, 67% of patients had eliminated or reduced medication dosage, 22% were on stable dosage, and 11% had increased or added medication.

LINAC radiosurgery, with appropriate equipment, technique and imaging, appears to be a safe, effective treatment modality for patients with medication-refractory TN. The majority of patients achieve pain relief and reduction in medication intake, with a low rate of minor complications. Further follow-up is required to assess the durability of these results.