Point: 1. Pyramids (corticospinal fibers)
Function:
Motor control of the opposite (contra.) side of the body
(arm, trunk, and leg).
Pathway:
Axons from cells in motor cortex course through the internal
capsule, cerebral peduncle (midbrain) and the basilar pons
to enter the pyramids on the ventral surface of the medulla.
In the caudal medulla the fibers decussate (pyramidal dec.)
and enter the lateral funiculus of the spinal cord as the
lateral corticospinal tract (L.C.S.T.).
Deficits:
Lesion rostral to pyramidal decussation (motor cortex,
internal capsule, cerebral peduncle, basilar pons, pyramid
of medulla) results in a contra. hemiplegia and Babinski;
lesion caudal to decussation (in spinal cord) results in
ipsi. hemiplegia and Babinski.
Other Note:
There is NO pronounced muscle atrophy following a lesion of
corticospinal fibers since they are UPPER MOTOR NEURONS.
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