Revision 5 for 'Lateral corticospinal tract'

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Lateral corticospinal tract

The lateral corticospinal tract is a descending neural pathway primarily concerned with motor function. There are separate lateral and anterior corticospinal tracts.

Gross anatomy

Central connections

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

Course

Organized somatotopically, these fibers 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 fibers 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.

Near the junction of the spinal cord and medulla, the majority (75-90%) of the corticospinal fibers decussate. This is where the lateral corticospinal tract separates from the anterior corticospinal tract.

Lateral corticospinal tract

The lateral corticospinal tract descends along the lateral funiculus. It lies anterolateral to the dorsal horn. The oval-shaped lateral tract is much larger than the anterior counterpart. The lateral tract however, also contains a small amount of neurons that have not decussated.

As it descends, the lateral corticospinal tract deviates to the dorsolateral surface of the spinal cord. At the same time, it diminishes in size. At approximately the fourth sacral level, it terminates entirely.

Related pathology

 

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