Initial clinical experience with surface image guided (SIG) radiosurgery for trigeminal neuralgia

Background: To evaluate the initial clinical experience with a surface image guided technique for stereotactic radiosurgery using minimal patient immobilization and real-time patient motion monitoring for the treatment of trigeminal neuralgia (TN). Methods: The study describes the first seven TN patients treated with this technique. Head positioning was achieved with a patient-specific head mold made out of expandable foam that conforms to the patient's occiput. The face of each patient was left open and unobstructed for maximal comfort. The motion of a region of interest consisting of the forehead, eyes, nose, and temporal bones was monitored during treatment using a video surface imaging system (Vision RT Ltd., London, UK). Initial setup of the patient was performed with the surface imaging system using the treatment planning computed tomographic (CT) scan. Initial setup was confirmed and finalized with cone-beam CT (CBCT) and KV X-ray images prior to treatment. The dedicated linear accelerator used for delivery was a Trilogy (Varian Medical Systems, Palo Alto, CA) with 5 mm collimator with 13 arcs. Patients were monitored during treatment with surface imaging cameras and software, equipped with a beam stop mechanism if the patient's motion was found to exceed a specified tolerance. Results: Seven patients with TN underwent single fraction radiosurgery to a dose range of 80-90 Gy with surface image guidance. All patients experienced pain relief. Four of the seven patients experienced complete resolution of pain. At a median follow-up of 31.4 months, two of seven patients developed pain recurrence. One patient reported intermittent facial numbness after SRS which resolved by 9 months post-treatment. Conclusions: The surface image guided technique using minimal immobilization and real time surface imaging has proven to be safe and effective in a small cohort of patients with TN. To our knowledge this is the first series describing the use of this technology in SRS for TN. Patient compliance is important, and appears improve given the speed and comfort of this technique. An additional degree of semi-rigid immobilization may be required in some patients.