pyramidal tract


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Related to pyramidal tract: pyramidal tract signs

py·ram·i·dal tract

[TA]
an imprecisely defined term, generally used to describe axons from the cerebral cortex that enter the pyramid thereby representing all corticospinal fibers rostral to the pyramidal decussation; when the term is used to describe the lateral corticospinal tract, this entity should be designated as the crossed pyramidal tract. See: corticospinal tract.
Farlex Partner Medical Dictionary © Farlex 2012

pyramidal tract

n.
A major pathway of the central nervous system, originating in the sensorimotor areas of the cerebral cortex and generally descending through the brainstem to the spinal cord. The fibers of the pyramidal tract transmit motor impulses that control voluntary movement.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

py·ram·i·dal tract

(pir-am'i-dăl trakt) [TA]
A massive bundle of fibers originating from pyramidal cells in the precentral motor and premotor area and in the postcentral gyrus. Fibers from these cortical regions descend through the internal capsule, the middle third of the crus cerebri, and the ventral part of the pons to emerge on the ventral surface of the medulla oblongata as the pyramis. Continuing caudally, most of the fibers cross to the opposite side in the pyramidal decussation and descend in the spinal cord as the lateral pyramidal tract, which distributes its fibers to interneurons of the spinal gray matter. Interruption of the pyramidal tract at or below its cortical origin causes impairment of movement in the opposite body-half, especially severe in the arm and leg and characterized by muscular weakness, spasticity and hyperreflexia, and a loss of discrete finger and hand movements. Babinski sign is associated with this condition of hemiplegia.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

pyramidal tract

The great inverted pyramid of motor nerve fibres descending from the motor cortex of the cerebrum through the internal capsule and down into the brainstem where the fibre bundles on each side cross to the other side. This is why a STROKE on the right side causes paralysis on the left side of the body.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
In other words, it uses a magnetic field to stimulate the cortical motor and spinal areas, and records the electrophysiological response of the pyramidal tract. Using various shaped coils to conduct a magnetic field, the examiner stimulates specific cortical or spinal areas and collects information regarding MEP, with surface electrodes applied on different muscles.
How plausible is it to suspect that the Greek hero might have been injured so badly as to have his pyramidal tract hurt, before the arrow that caused his death?
Isaza Jaramillo SP, Uribe Uribe CS, Garcia Jimenez FA, Cornejo-Ochoa W, Alvarez Restrepo JF, Roman GC (2014) Accuracy of the Babinski sign in the identification of pyramidal tract dysfunction.
In these cases, ipsilateral 6th nerve palsy may be accompanied by contralateral lower and/or upper limb paresis resulting from partial or complete involvement of the pyramidal tract (Raymond syndrome), with Bells palsy on the ipsilateral side from involvement of deeper portions of the 7th nerve (Millard-Gubler syndrome).
Atrophy is widespread, leading to the term multiple system, suggesting that signs and symptoms can vary considerably.[5] The three major features of MSA are parkinsonism, cerebellar dysfunction, and autonomic dysfunction.[6] Pyramidal and extrapyramidal signs are often also present, whereas in IPD, pyramidal tracts are not affected.
It is believed that posed (voluntary) expressions are regulated by the pyramidal tracts of the facial nerves that descend from the cortex.
Subsequently, he presented with multiple cranial nerve palsies (from III to X cranial nerves) and central spastic palsy (bilateral pyramidal tracts involvement), which may suggest a brainstem insult.
The physiological classifications include spastic (increased muscle tone causing stiffness so that movement is difficult to control), caused by damage to the pyramidal tracts: nerve cells or fibers originating in the top of the brain.
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.