Illustrated Encyclopedia of Human Anatomic Variation: Opus III: Nervous System: Brain
Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed
The left pyramid decussates first in about 73% of individuals. Interesting variations in the pyramidal tracts have been reported. In about 71% of 144 specimens, both crossed and uncrossed pyramidal tracts were present bilaterally. In 13%, only crossed tracts were present; in 12%, both crossed tracts and one uncrossed tract were present; in 2.8%, only uncrossed tracts were found; and in 0.7%, one pyramid was totally crossed, and the other pyramid was totally uncrossed.
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