Origin of the ventral external arcuate fibers and their continuity with the striae medullares of the fourth ventricle of man

Abstract

) on the course of the medullary striae of Piccolomini of the fourth ventricle (long known as striae medullares acusticae) of the human brain, in which emphasis is placed on their cerebellar relations, brings up again their probable continuity with the ventral external (crossed) arcuate fibers and hence the origin and course of the latter. Apparent continuity of the ventral external arcuate fibers with the medullary striae, via fibers in the raphe, has been noted repeatedly, especially since the advent of the Weigert method. Kolliker (1896) illustrated this very clearly and naturally concluded that the medullary striae of the fourth ventricle serve to relate the cerebellum to the arcuate nuclei. The series described by Alphin and Barnes strongly suggest that some of these fibers continue into the cerebellum in the neighborhood of the stalk of the flocculus and that the rest end or begin in the region of the pontobulbar body.Both origin and termination in the cerebellum hare been claimed for these striae. Riley ('43) therefore designates them "striae rerebellares (ventriculi quarti) ." Spiegel and 325

Hypertrophy of the Anterior External Arcuate Fasciculus: A Rare Variant With Implications for the Development of the Arcuate Nucleus

“…It also had been recognized, however, that the rhombic lip is the origin of neurons not only of the basis pontis, but also the ION and AN (Essick, 1912;Rodriguez and Dymecki, 2000;Gilthorpe et al, 2002), that the AN and ION neurons begin migration prior to the pontine neurons, and that the neurons of the AN may bear a closer relationship to the ION neurons. Both ION and AN neurons migrate over the lateral and ventral surface of the medulla in a path that resembles the AEAF (Essick, 1912;Rasmussen and Peyton, 1946;Filiano and Kinney, 1992). Immunohistochemical analysis also has been used to study the origin of the AN in the FIGURE 7 | Axonal density in the medullary pyramid (left panel) and the AEAF (right panel).…”

“…There are two main projection pathways for axons from the AN. Some axons from the AN project anteriorly onto the ventral surface of the medulla in the anterior external arcuate fasciculus (AEAF), which traverses the inferior olive as a circumolivary bundle and ultimately projects to the cerebellum via the inferior cerebellar peduncle; others project posteriorly into the medullary reticular formation (Rasmussen and Peyton, 1946;Zec et al, 1997;Fu and Watson, 2012). In the mouse, the cerebellar target of the AN-like structure is the paraflocculus of the contralateral cerebellar cortex (Fu and Watson, 2012).…”

“…The AEAF is a bundle of axons on the ventral surface of the medulla that arises predominantly from the AN (Rasmussen and Peyton, 1946;Zec et al, 1997;Gray et al, 2005;Fu and Watson, 2012). It begins as a midline fiber bundle and travels along the ventral and lateral subpial surface of the medulla, crosses over the surface of the inferior olive as the circumolivary bundle, and enters the inferior cerebellar peduncle to terminate in the cerebellum, although the exact cerebellar termination has not been fully determined in humans (Rasmussen and Peyton, 1946;Gray et al, 2005;Rubens and Sarnat, 2013). Dye-tracking studies have identified the AEAF as a band of fibers located along the entire extent of the ventrolateral surface of the medulla at the level of the ION that forms an arching bundle of fibers (Zec et al, 1997).…”

Proceedings from the First International Symposium on the Congenital Central Hypoventilation Syndrome held in New Orleans, LA, on May 11, 1996

“…Historically, this nucleus has been considered a relay nucleus from the cerebral cortex to the cerebellum via the external arcuate fibers and inferior cerebellar peduncle. 44 In a comparative anatomic study between the human infant and cat VMS, we found that the arcuate nucleus, nucleus conterminalis, and foci of thickened marginal glia in the human are anatomically homologous to the cat RCFs. 45 This homology is based on cytoarchitectonic criteria (including cell size, shape, and distance from the surface), as defined in the combined neuroanatomic and physiologic studies of the cat RCFs of Trouth et al, 41 Schläfke et al, 35 and others [37][38][39][40][41][42][43] , and on three-dimensional cell distributions, as determined with the aid of computer reconstructions.…”

Individual variability in the size and organization of the human arcuate nucleus of the medulla

“…Classically, the Arc is considered a precerebellar relay nucleus, similar to the pontine nuclei, with input from the cerebral cortex and projections to the cerebellum via the inferior cerebellar peduncle (Olszewski and Baxter 1982;Rasmussen and Peyton 1946). A totally different view of the Arc has been proposed on the basis of neuropathological observations showing aplasia of the Arc in the brains of children who died of SIDS (Sudden Infant Death Syndrome).…”