Gyroscopic Radiosurgery for the Treatment of Trigeminal Neuralgia

Radiosurgical treatment of trigeminal neuralgia (TN) is the most common functional radiosurgery procedure used to modulate refractory pain. The aim of this study is to describe the clinical results and dosimetric parameters of the first series of patients with TN treated with ZAP-X gyroscopic frameless radiosurgery (ZAP Surgical Systems, Inc., San Carlos, CA), an innovative, frameless radiosurgical device.

A total of 30 patients with TN received gyroscopic frameless radiosurgery (GRS) between February 2023 and January 2025. Treatment plans were developed delivering a maximum dose of 90 Gy in a target that covered a 5-mm segment of the trigeminal nerve in the retrogasserian location using a single isocenter (5 mm collimator). Clinical and treatment information were analyzed with a specific focus on demographic characteristics, etiology, previous treatments, Barrow Institute (BNI) Pain Intensity Scale before and after GRS (pain relief response), the time to pain relief, and the rate of complications and recurrences.

30 patients (21 females and 9 males) with a median age of 66 years (range: 31-92 years) underwent GRS for refractory TN. The median time from first diagnosis to GRS was 4 years (range: 6 months to 18 years). All patients had received a first therapeutic pharmacological line, 15 patients received at least a radiofrequency thermocoagulation, 7 patients received nerve blocks, 4 patients were treated with botox injection and 2 patients had previous radiosurgery. The median BNI Pain Intensity Scale before GRS was IV (range IIIa-V). The median treatment time was 37 minutes using a median of 221 beams. Median V12 and V10 of the brainstem were 0.04cc (range: 0-0.16cc) and 0.07cc (range: 0-0.24cc), respectively. The median BNI Pain Intensity Scale after GRS was II (range: I-VI) with 80% of patients reporting no pain or occasional pain without medication. The median time to pain relief was 15 days (range: 1-60 days). Five patients (16.6%) presented ipsilateral facial hypesthesia after GRS. 10% of patients presented with recurrent pain 2-6 months after GRS.

GRS is a precise tool for treating TN, demonstrating safety and effectiveness in what is, to our knowledge, the first reported case series documenting its use.