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

A tract of nerve cells that carries motor commands from the brain to the spinal cord.
Mentioned in: Neurologic Exam
References in periodicals archive ?
The pyramidal tract was found in 61% of all operated patients, so it can be considered as a normal component of the thyroid gland and not as ectopic tissue.
Preoperative assessment of motor cortex and pyramidal tracts in central cavernoma employing functional and diffusion-weighted magnetic resonance imaging.
Intraoperative diffusion-weighted imaging for visualization of the pyramidal tracts. Part II: clinical study of usefulness and efficacy.
Clinical evaluation and follow-up outcome of diffusion tensor imaging-based functional neuronavigation: a prospective, controlled study in patients with gliomas involving pyramidal tracts. Neurosurgery 2007; 61:935-948.
The mean distance between the stimulation sites and the DT-imaged fiber tracks varies from 2mm to 1cm in the pyramidal tract [3,16,18,24] and to visualize language-related subcortical connections, such as the arcuate fasciculus (AF) distances between the stimulus points and the AF were within 6 mm [10].
Intraoperative diffusion-weighted imaging using an intraoperative MR scanner of low magnetic field strength (0.3 Tesla) has been developed demonstrating clinical usefulness and efficacy in detecting the pyramidal tract and its relationship with tumor borders [26].
Diffusion-tensor imaging-guided tracking of fibers of the pyramidal tract combined with intraoperative cortical stimulation mapping in patients with gliomas.
Intraoperative three-dimensional visualization of the pyramidal tract in a neuronavigation system (PTV) reliably predicts true position of principal motor pathways.
Three-dimensional visualization of the pyramidal tract in a neuronavigation system during brain tumor surgery: first experiences and technical note.
Non-spastic cerebral palsy is due to damage to nerve cells outside of the pyramidal tracts. These are extra-pyramidal systems that aid in coordinating movement.
Diffusion tensor imaging in chronic subdural hematoma: correlation between clinical signs and fractional anisotropy in the pyramidal tract. An J Ne uroradiol.