The emissary veins of the foramen ovale: an anatomical study using magnetic resonance imaging

Purpose The emissary veins (EVs) passing through the foramen ovale (FO) are not well understood. The aim of this study was to characterize these veins using contrast magnetic resonance imaging (MRI). Methods In total, 85 patients underwent thin-sliced, contrast MRI. Coronal and sagittal images were used for the analysis. Results The EVs of the FO were well delineated in 100% on sagittal and 97% on coronal images. On the sagittal images, these veins could be classified into the lateral, medial, and perineural types in association with the mandibular division of the trigeminal nerve (V3) segment in the FO. In 22% of the slides, the medial EV was more predominant than lateral one, while in 64% of the slides, the latter was more predominant. On the coronal images, the identified EVs of the FO coursed medially to the V3 in 68% and laterally in 72% of 165 sides. The perineural EVs most frequently coursed along both the lateral and medial surfaces of the V3. On the sagittal images, the angles formed by the midline of the V3 segment in the FO and lower margin of the FO were 81.5 +/- 11.9 degrees on the left side and 80.0 +/- 12.2 degrees on the right, while on the coronal images, they were 61.5 +/- 12.1 degrees on the left side and 64.8 +/- 11.3 degrees on the right. Conclusions The EVs of the FO are structures that may be characterized by a well-developed venous channel in the lateral aspect of the V3 and nearly symmetrical orientation of both V3s lying in the FO.