Anatomy of the Rostral Nucleus of the Solitary Tract

Abstract

The nucleus of the solitary tract (NST) is a major sensory nucleus in the dorsal medulla that receives cardiovascular, visceral, respiratory, gustatory, and orotactile information [1,2]. The NST begins at the level of the pyramidal decussation near the cervical spinal cord and extends rostral to the caudal part of the dorsal cochlear nucleus [3]. Caudally, the NST spans the midline forming the commissural subnucleus. Rostral to the area postrema, the NST splits into left and right halves that straddle the midline and abut the ventrolateral edge of the fourth ventricle. The traditional anatomical beginning of the rostral NST (rNST) is the point where the medial edge of the nucleus no longer contacts the fourth ventricle (Figure 2.1). The rNST initially is displaced laterally from the fourth ventricle by the medial vestibular and prepositus hypoglossal nuclei and at its rostral extreme is adjacent to the spinal trigeminal and vestibular nuclei. Although histologically contiguous with the caudal part of the nucleus, the rNST is functionally distinct because it receives gustatory and other orosensory primary afferent input [4,5]. In fact, the traditional anatomical location of the border between the rostral and caudal NST only partly reflects the functional differences between these regions of the nucleus. Because terminal fields of orosensory cranial nerves extend several hundred microns caudal to where the NST moves lateral to the fourth ventricle [6–10], functionally the rNST extends caudal to its traditional beginning.