decussatio

(de-kfi-sa's hyo) [L.] Decu ation, d. bra'chi i conjunct i'vi [BNA], a cro ing of the fiber tracts of the tegmenta, originating from the brachia conjunctiva, behind the red nucleus. d. fontina'lis, fountain decu ation, a ma of fibers between the red nuclei, arising from the cells of the nates or colliculus superior of the corpora quadrigemina and the central gray layer on either side; the fibers cro in the middle line and join the medial longitudinal fasciculus on the opposite side. d. lemnisco'- rum [BNA], decu ation of the lemniscus or fillet, sensory decu ation of the medulla oblong at a, an intercro ing of fibers in the median plane of the medulla or the dorsal aspect of the pyramids, immediately above the level of the decu ation of the pyramids, d. nervo'rum trochlear'ium [BNA], the cro ing of the fibers of the two trochlear nerves on the upper surface of the velum meduUare anterius. d. pyram'idum [BNA], decu ation of the pyramids, the intercro ing of the bundles of the cro ed pyramidal tracts at the lower part of the medulla oblong at a, d. tegmen to'rum [BNA], decu ation of the tegmenta, a cro ing of the fiber tracts of the tegmenta lying nearest the median line in the region below the aqueduct where the tegmenta are united.