corticospinal tract

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cor·ti·co·spi·nal tract

a composite bundle of corticospinal fibers [TA] that descend into and through the medulla to form the lateral corticospinal tract [TA] and the anterior corticospinal tract [TA]. This massive bundle of fibers originates from pyramidal cells of various sizes in the fifth layer of the precentral motor (area 4), the premotor area (area 6), and to a lesser extent from the somatosensory cortex. Cells of origin in area 4 include the gigantopyramidal cells of Betz. Fibers from these cortical regions descend through the internal capsule, the middle third of the crus cerebri, and the basilar pons to emerge on the anterior surface of the medulla oblongata as the pyramid. Continuing caudally, most of the fibers cross to the opposite side in the pyramidal (motor) decussation and descend in the posterior half of the lateral funiculus of the spinal cord as the lateral corticospinal tract, which distributes its fibers throughout the length of the spinal cord to interneurons of the zona intermedia of the spinal gray matter. In the (extremity-related) spinal cord enlargements, fibers also pass directly to motoneuronal groups that innervate distal extremity muscles subserving particular hand-and-finger or foot-and-toe movements. The uncrossed fibers form a small bundle, the anterior corticospinal tract, which descends in the anterior funiculus of the spinal cord and terminates in synaptic contact with interneurons in the medial half of the anterior horn on both sides of the spinal cord. Interruption of corticospinal fibers rostral to the motor (pyramidal) decussation causes impairment of movement in the opposite body-half, which is especially severe in the arm and leg and is characterized by muscular weakness, spasticity and hyperreflexia, and a loss of discrete finger and hand movements. Lesions of lateral corticospinal fibers caudal to the motor decussation result in comparable deficits on the ipsilateral side of the body. The Babinski sign is associated with this condition of hemiplegia.
Farlex Partner Medical Dictionary © Farlex 2012

Corticospinal tract

A tract of nerve cells that carries motor commands from the brain to the spinal cord.
Mentioned in: Neurologic Exam
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Intraoperative neurophysiological monitoring of the spinal cord during spinal cord and spine surgery: a review focus on the corticospinal tracts. Clin Neurophysiol.
Motor outcome according to the integrity of the corticospinal tract determined by diffusion tensor tractography in the early stage of corona radiata infarct.
However 44 students in test group were allowed to use the Pyrimidal corticospinal tract educational aid (both the model and computer animation) during their small group discussion time.
In particular, we found that fornix MRI indices were associated with PASAT-3 scores, whereas corticospinal tract MRI indices were not.
Additional characteristics include axonal loss within the descending pyramidal tracts as well as myelin pallor and gliosis in the corticospinal tracts. LMN pathology affects the anterior horn motor cells of the spinal cord and brainstem.
[19] reported that WD in the corticospinal tract was associated with motor dysfunction at 30 days following middle cerebral artery ischemic stroke.
In another study [72], optogenetic stimulation of the intact corticospinal tract was sufficient to promote functional recovery after a large photothrombotic stroke in rats.
It is considered that a damaged central nervous system will never be restored [1], but we reported that the once paralyzed motor function of the forelimbs of juvenile rats had been restored due to a significant change that occurred in the corticospinal tract pathways after a brain injury [2].
For a long time, the view of cervical hyperextension violence resulting in corticospinal tract injury leading to CCS has been widely accepted.
Inhibition of the corticospinal tract is generally thought to cause spasticity, but over the years it has been noted that there are many examples of corticospinal tract injuries where patients do not present with spasticity, but reduced tone.
In humans, the corticospinal tract extends from the cerebral cortex in the upper brain down into the spinal cord.