Medulla oblongata: Vagus nerve level (Latin)

At this level, the canalis centralis opens into the ventriculus quartus, forming the pars superior medullae oblongatae. A part of the n. vagus can be seen extending from the ncl. posterior nervi vagi, while the remainder arises primarily from the ncl. ambiguus. Medial to the ncl. posterior nervi vagi are the ncl. nervi hypoglossi and ncl. subhypoglossalis (of Roller). Laterally, the nuclei of the funiculus posterior terminate in order to make room for the ncl. vestibularis medialis. The pedunculus cerebellaris inferior begins to appear at this level and is surrounded by many nuclei. A prominent feature of this level is the large formatio reticularis, which lies anterior to the ncl. nervi hypoglossi and ncl. posterior nervi vagi, lateral to the fasciculus longitudinalis medialis and tractus tectospinalis and overlaps the ncl. ambiguus. At this level, the ncl. olivaris inferior principalis begins to expand resulting in an external prominence on the anterolateral surface of the medulla oblongata known as the olive (oliva). The ncll. olivaries accessorii medialis et posterior can be identified medial and posterior to this structure. Towards the midline of the medulla oblongata, decussating fibres of the lemniscus medialis form a seam known as the raphe. On either side of the raphe are a cluster of neurons, the ncll. raphes, which belong to the formatio reticularis medullae oblongatae. The fasciculus longitudinalis medialis can also be identified along the raphe. This white matter tract ascends through the brainstem along its dorsal midline, while the tractus spinothalamici et spinocerebellares maintain their anterolateral position, just dorsal to the olive (oliva).