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.

corticospinal tract

any of two groups of nerve fibers (the anterior corticospinal tract and lateral corticospinal tract) that originate in the cerebral cortex and run through the spinal cord. They are responsible for carrying motor fibers.

Corticospinal tract

A tract of nerve cells that carries motor commands from the brain to the spinal cord.
Mentioned in: Neurologic Exam
References in periodicals archive ?
8] divided WD in the corticospinal tracts into 4 stages according to dynamic signal intensity changes on MRI: Stage 1 (within 4 weeks) exhibited no signal intensity abnormality; Stage 2 (4-14 weeks) exhibited hypointense signals on T2WI; Stage 3 (14 weeks to several years) presented hyperintense signals on T2WI; and Stage 4 (several years later) exhibited shrinkage of the white matter fiber tracts with volume loss.
Three-dimensional white matter tractography by diffusion tensor imaging in ischaemic stroke involving the corticospinal tract.
Incorporating functional MR imaging into diffusion tensor tractography in the preoperative assessment of the corticospinal tract in patients with brain tumors.
1-3) Normal fiber tracts are also seen in the brainstem (including the corticospinal tracts, medial lemnisci, and superior, middle and inferior cerebellar peduncles).
A recent study reported that after midthoracic dorsal hemisection, the corticospinal tract collaterals of the hind limb sprout into the cervical gray matter where they contact descending propriospinal neurons and a new intraspinal circuit is formed [22].
Clearly, knowledge of the location of the corticospinal tract in such a case would be advantageous, since the neurosurgeon would not have to perform a craniotomy, operate on the brain, and perform direct white matter stimulation only to discover that the tumor is inoperable.
A recent study examined the effects of OEC transplantation into the dorsal transected spinal cord, which transects the dorsal corticospinal tract on apoptosis and neuronal death in the primary motor cortex (M1) [44].
The optic nerve, like the corticospinal tract (or primary motor tract) within the spinal cord, consists only of mytelinated fibers and thus provides a tractable system in which secondary injury of white matter can be readily studied.