TOPOGRAPHICAL ANATOMY OF THE POSTERIOR COLUMNS OF THE SPINAL CORD IN MAN

Nine cases are presented which illustrate the segmental anatomy of the posterior columns with respect to the long ascending fibres. It is concluded that the fasciculus gracilis (FG) and the fasciculus cuneatus (FC) should be considered as separate anatomical entities. It is shown that the shape of each fasciculus is different in, and characteristic of, each of the upper thoracic and cervical segments. A certain degree of segmental lamination is present in the FG, but with extensive overlapping of fibres from different segments. The orientation of the laminae is not the same in all segments, being very approximately parallel to the medial border of the posterior horn in most caudal segments, approximately parallel to the median septum in intermediate segments, and oblique in an anteromedial posterolateral direction in cranial sections. The pattern of lamination in the FC and the degree of overlapping of fibres resembles that in the caudal FG. There is no, or minimal, overlapping of fibres of the FC with those of the FG. The most medial fibres of the FC, lying along the lateral border of the FG, are in proximity with fibres, in that fasciculus, from many different segments.