A Standardized Method for Sphenopalatine Ganglion Localization Using VIDIAN Canal Landmarks on High-Resolution MRI

Introduction: The sphenopalatine ganglion (SPG), also known as the pterygopalatine ganglion, is a key parasympathetic relay within the pterygopalatine fossa (PPF) and has emerged as a neuromodulatory and radiosurgical target for refractory craniofacial pain syndromes. Despite increasing relevance, a standardized method for SPG localization remains undefined. Given its small size and proximity to the maxillary nerve (V2), internal maxillary artery, and osseous margins of the PPF, accurate targeting requires an anatomy-driven approach. We describe a reproducible MRI-based guideline for identifying the isocenter of the SPG, using the vidian canal as a reliable landmark, with cadaveric validation. Methods/Approach: Thin-slice FIESTA MRI was reviewed to establish consistent anatomical landmarks. Localization began with the identification of the foramen rotundum and anterior tracing into the PPF. Fibers coursing laterally were recognized as maxillary nerve (V2) divisions, whereas medial–inferior fibers were followed to converge into the SPG. Tracing these medial–inferior fibers demonstrate their convergence into an ovoid neural structure positioned immediately anterolateral to the vidian canal, which serves as the key landmark for localization of the ganglion. Contours were drawn circumferentially at this level and extended when margins remained distinct. The methodology was cross-validated with CT osseous anatomy and confirmed by cadaveric dissection, demonstrating high concordance between imaging-based contours and gross anatomic SPG position. Conclusion: We present a practical, anatomy-based guideline for SPG contouring on FIESTA MRI, anchored to vidian canal landmarks and validated by CT correlation and cadaveric dissection. Standardizing SPG localization may improve accuracy in radiosurgical planning and provide a foundation for future clinical studies targeting craniofacial pain. Fig. 1 Sample MRI with SPG Contoured Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany