1286. Using Computed Tomography Imaging to Assess Percutaneous Trajectory for Accessing the Foramen Ovale

Authors: William Kyle Miller; Tamara Maghathe, MS; Andrew Caras, BS; Tarek Mansour, MD; Luke Mugge, BS; Jason Schroeder, MD (Toledo, OH)

Introduction: Percutaneous treatments, including balloon compression rhizotomy, are reasonable options for patients suffering from trigeminal neuralgia (TGN). Current literature describing percutaneous foramen ovale (FO) access is based upon dry skull and formalin-fixed specimen measurements. This study aims to better define parameters for intraoperative percutaneous FO access via a novel CT imaging and image guidance software method. Methods: 30 randomly-selected head and neck soft-tissue CTs of patients without TGN were analyzed. Percutaneous rhizotomy trajectories were created bilaterally by measuring a point 2.5 cm lateral to the oral commissures (entry point) and connecting a straight line to the ipsilateral FO. Angles and distances related to anatomy and surgical approach were measured using image guidance software. Results: Mean calculated FO width was 4.06 ± 0.80 mm (left) and 4.06 ± 0.75 mm (right). Mean angles were assessed bilaterally: surgical trajectory and orbital roof, 61.96 ± 6.87° (left) and 61.25 ± 6.79° (right); trajectory and sagittal-midline plane, 18.67 ± 3.48° (left) and 19.27 ± 4.33° (right); trajectory and palate, 40.29 ± 4.92° (left) and 40.63 ± 5.14° (right). After controlling for age, BMI (mean 30.3 ± 6.3) does not independently correlate with angle from midline on left (p = 0.508) or right (p = 0.289). Conclusion: Angles created by trajectory for trigeminal rhizotomy determined by CT are similar to the literature for angle with midline (approximately 20°) and angle with the palate (approximately 45°). Similar angle from midline across BMIs suggests this technique is useful for a variety of body habitus. Angle of trajectory and orbital roof was obtained because it is easily visualized on intraoperative fluoroscopy. Soft tissue CT permitted accurate representation of a patient, in contrast to formalin-fixed and dry skulls. Defining accurate needle trajectory values will ideally improve surgeon confidence in accessing the FO percutaneously.