The anterior corticospinal tract is formed at the level of the of the medullary pyramids, where the majority (90%) of descending corticospinal tract fibers decussate to form the lateral corticospinal tract. The majority of the remaining non-decussating 10% of fibers form the much smaller anterior corticospinal tract 1,2.
It descends in the anterior funiculus of the spinal cord, lying close to the anterior median fissure. At each relevant level, fibers cross the anterior spinal commissure of the spinal cord to synapse with ventral horn motor neurons. The anterior corticospinal tract thus becomes smaller as it descends, ending at the level of the mid-thoracic cord.
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Variant anatomy
In some cases, the anterior corticospinal tract is absent. In rare cases, this tract may contain all corticospinal fibers.
Function
The anterior corticospinal tract is primarily responsible for gross and postural movement of the trunk and proximal musculature 3.
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