A Novel Method of Locating Foramen Ovale for Percutaneous Approaches to the Trigeminal Ganglion.

BACKGROUND: For patients with trigeminal neuralgia who do not respond to medication and for whom surgical approaches are too risky, percutaneous procedures targeting the trigeminal ganglion are the current standard treatment. Percutaneous procedures are performed via the transoval approach under radiologic guidance. Identification of the foramen ovale (FO) under fluoroscopic guidance is an important part of determining the success or failure of the procedures. OBJECTIVES: Previous studies have described how to visualize the FO under fluoroscopic guidance, but those methods are limited by poor reproducibility. In this study, we have investigated how to visualize the FO clearly and easily under fluoroscopic guidance. STUDY DESIGN: Retrospective analysis. SETTING: University hospital in Korea. METHODS: Seventy-two 3-dimensional facial computed tomography scans without anatomic abnormalities of the skull base were analyzed for verifying the novel method. First, the mandibular angle and the occipital cortical line were overlapped and then turned by 15° oblique rotation using the software package. After these manipulations, the visualization of the FO was graded according to a 4-point scale (0: poor; 1: fair; 2: good; 3: excellent), and the inferior transfacial and oblique angles were measured. RESULTS: This enabled clear visualization of the FO. The mean visual grade of 54 right and 46 left FO (total 100) was 2.74 (0: poor; 1: fair; 2: good; 3: excellent). All recorded FOs had at least grade 2 visibility. LIMITATIONS: This study is lacking application in clinical practice and comparative data to the submental view. CONCLUSIONS: The mandible angle and the occipital cortex line are obvious anatomic landmarks and are visible even to nonexperienced practitioners. Therefore, our method using these anatomic landmarks can improve the reproducibility and accuracy of FO visualization. KEY WORDS: Trigeminal neuralgia, foramen ovale, trigeminal ganglion, 3-dimensional (3D) facial computed tomography (CT) scans.