Novalis LINAC Radiosurgery for Trigeminal Neuralgia
A. Chawla, M.D., K. Kappeler, R. Siddon, Ph.D., T. Eckel, M.D., T.Burke, M.D.
Departments of Radiation Oncology, Radiology, and Neurosurgery
Center for Facial Pain, Anne Arundel Medical Center, Annapolis, MD
Background: Trigeminal Neuralgia (TN) is a rare pain disorder with a profound impact on quality of life. For patients with medication-refractory TN, stereotactic radiosurgery (SRS) directed at the affected nerve root is a viable local treatment option. The majority of published data deals with Gamma Knife technology. Linear accelerator (LINAC)-based SRS, with appropriate and reproducible isocenter stability provided with the Brainlab Novalis system, can be utilized but data in this regard is more limited.
Purpose: Our objective was to determine the results of LINAC radiosurgery in the management of TN at a single institution.
Methods: Between January 2004 and February 2006, 18 patients with unilateral TN, medication-refractory, 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 was performed for localization of the trigeminal nerve. Axial acquired T1-weighted 3D spoiled gradient echo (SPGR) images were obtained after IV gadolinium administration, supplemented by multi-slab axially acquired 3D fast spin echo T2-weighted images to localize the nerve in the para-pontine cistern. Utilizing Brainlab Novalis software, fusion was performed between these MRI images and treatment-planning CT obtained the day of treatment delivery.
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. Isocenter stability was estimated at <0.5 mm using the Winston-Lutz test.
Pain response was recorded at initial 4-8 week follow-up, and serially at 3-month intervals via pain intensity score (0 to 10), frequency, and duration. Pain response was categorized as: none, minimal (< 50%), partial (>50%), or complete (100%). Complications and alterations in pain medication intake were also tabulated at each visit.
Results: Of 18 patients treated, 17 (94%) achieved at least a partial response to treatment, at a median time of 4 weeks from SRS delivery. At a median follow-up of 12 months from treatment, the actuarial rate of pain recurrence or persistence was 28%. No complications were noted from radiotherapy delivery, but 17% of patients reported scalp pain at pin sites, which resolved within a few weeks in all cases. At most recent follow-up, 67% of patients had eliminated or reduced medication dosage, 22% were on stable dosage, and 11% had increased or added new medication.
Conclusions: Novalis LINAC radiosurgery, with appropriate technique and delivery, appears to be a safe and initially effective treatment modality for patients with medication-refractory TN. Results are comparable to that achieved with Gamma Knife radiosurgery. The majority of patients did achieve pain relief and subsequent reduction in pain medication intake. Further follow-up will be required to assess the long-term durability of these results.
Updated 7-14-06