Fluoroscopic Landmark to Optimize the View of the Foramen Ovale Using the Neighboring Structure

Abstract

Radiofrequency thermocoagulation (RFT) via trans-oval approach is effective treatment modalities for trigeminal neuralgia. Clear identification of the foramen ovale (FO) is the most important initial step for successful percutaneous procedures. The purpose of this study was to verify whether the medial end of the temporomandibular joint and the distance between the mandibular angle and the occipital inner line can be used as a fluoroscopic landmark to determine the proper angulation of the C-arm. Analysis of previously saved fluoroscopic FO images during RFT was performed. As a fluoroscopic landmark to guide a proper lateral and axial oblique rotation of the C-arm, the position of the medial end of the temporomandibular joint and the vertical distance between the mandibular angle and the occipital inner line were evaluated. When the FO was located at the most central point within the H-figure, the medial end of TMJ was always located within the mandibular notch. The maximum view of the FO was defined when the FO showed maximal short axis to long axis ratio. The FO showed the best view when the vertical distance between the mandibular angle and occipital inner line was 20.04 (5.1) mm. This study demonstrated that the medial end of the temporomandibular joint and the vertical distance between the mandibular angle and occipital inner line as a fluoroscopic landmark for obtaining the optimal view of the FO.