Anterior corticospinal tract

The anterior corticospinal tract is a descending neural pathway primarily concerned with motor function. There are separate lateral and anterior corticospinal tracts as fibres decussate at the cevicomedullary junction.

Gross anatomy

Central connections

Corticospinal fibres arise from neurons in the cerebral cortex. Most of these arise in the primary motor and pre-motor cortices. In the primary motor cortex, fibres arise specifically from Betz cells. The somatosensory and the nearby parietal cortices supply a small number of fibres. 

Course

Organised somatotopically, these fibres descend through subcortical white matter. Following descent through the anterior two-thirds of the posterior limb of the internal capsule, they pass through the ventral midbrain, specifically the central and lateral portions of the inner crus, and continue through the pons. In the medulla oblongata, corticospinal fibres collect into a discrete bundle. This bundle forms the pyramid.

The pyramid is a discrete triangular column on the ventral medulla oblongata next to the midline. This is why the corticospinal tract is also called the pyramidal tract. Within the pyramids, the majority (75-90%) of the corticospinal fibres decussate. This is where the anterior corticospinal tract separates from the lateral corticospinal tract.

Anterior corticospinal tract

The anterior corticospinal tract is comparatively small in relation to the lateral corticospinal tract. The anterior corticospinal tract descends in the anterior funiculus of the spinal cord. It lies close to the anterior median fissure.

The anterior corticospinal tract becomes even smaller while descending. These fibres cross the median plane & connect with contralateral neurons at the site of termination. By the level of the mid thoracic cord, this tract disappears.

Variants

In some cases the anterior corticospinal tract is absent. In rare cases, this tract may contain all corticospinal fibres.

Related pathology


Spinal anatomy
Neuroanatomy
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Article Information

rID: 47408
Section: Anatomy
Synonyms or Alternate Spellings:

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