The rubrospinal and central tegmental tracts in man.

Ten cases are presented which illustrate aspects of the anatomy of the rubrospinal and central tegmental tracts in man. It is concluded that the number of large fibres arising from the magnocellular part of the red nucleus and constituting the classical rubrospinal tract is small and that only a few fibres project into the spinal cord; these cannot usually be traced caudal to the upper cervical segments. There is a very large number of rubro-olivary fibres arising from the parvocellular part of the red nucleus, which run in the central tegmental tract. This tract also contains descending fibres that do not originate in the red nucleus and fibres that do not terminate in the olive. The literature on the rubrospinal tract and the rubro-olivary component of the central tegmental tract in primates in reviewed. Comparative anatomical studies are also briefly reviewed; they accord with the findings reported here for man.