Point 1


Intro

Pathway

Deficits

Clinical

Note

Summary

Overview

Problems


Contents

Anatomy

 

 

Let's review! The cells of origin of the corticospinal tract lie in the ipsilateral cerebral cortex. In contrast, the cells of origin of the lateral corticospinal tract lie in the contralateral cerebral cortex. REMEMBER--the lateral corticospinal tract is the part of the corticospinal system in the spinal cord. It is important to remember that damage to the corticospinal fibers rostral to the pyramidal decussation results in contralateral motor deficits, while lesions in the spinal cord (i.e., caudal to the decussation) result in ipsilateral deficits. Clinicians refer to the motor deficit resulting from a lesion of the corticospinal tract as hemiplegia (plegia =paralysis). For instance, they would say that a lesion of the LEFT corticospinal tract in the internal capsule (rostral to the pyramidal decussation) results in a RIGHT hemiplegia (involves the right arm, trunk and leg) while a lesion of the LEFT lateral corticospinal tract at C1 (in the spinal cord and therefore caudal to the decussation) results in LEFT hemiplegia.

A unilateral lesion of the lateral corticospinal tract results in motor deficits ipsilateral to the lesion. Interrupting the tract does NOT result in muscle atrophy, since the neurons innervating muscle are NOT dead. For example, if the LEFT lateral corticospinal tract is interrupted at Cl, then the LEFT arm, trunk and leg are affected. This is because the lateral corticospinal tract influences the musculature on the same (ipsilateral) side of the body. If the lesion involves the LEFT lateral corticospinal tract at T3, then only the LEFT trunk and leg are affected, since the spinal cord motor neurons that innervate the muscles of the arms still receive corticospinal input.