Patterns of pyramidal decussation and their relationship to handedness.

Adult medullae (158) were dissected and the patterns of decussation described grossly and correlated with microscopic findings. The top level or first crossing appeared from the left to the right in 73%, right to the left in 17%, and no preference was seen in 10%. A correlation with handedness was attempted, and the trend of these data suggests that there is no difference between the right and left handers in their pattern of crossing, although the number of left handers in the sample is small. Variations of pyramidal decussations appear to be great, but the major categories appear to be the large bundles with distinct preference at the first level of crossing and crowded small bundles on the top. There are also further subdivisions.(24:326-332,1971) Key Words.— Pyramidal decussation; handedness; cerebral asymmetry; cerebral dominance; anatomy of the medulla oblongata.