corticospinal tract

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Related to Pyramidal signs: pyramidal tract signs, akinetic mutism

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 ?
In the absence of other known neurologic conditions, the presence of at least one reproducible pyramidal sign and the presence of cord compression and T2 WI HI will significantly increase the likelihood of myelopathy.
Hemiplegia as an initial manifestation of JE is an unusual phenomenon and symptoms like tremors, rigidity, thick slurred speech may be initial features, but more frequently, choreoathetosis and other extra pyramidal signs become evident in the second week of illness (1).
Absent bulbar and pyramidal signs, and lack of spreading to the other limbs after 4 years, distinguish MMA from a monomelic onset of ALS (6).
She only presented with a brisk deep tendon reflex in the lower limbs, representing a slight pyramidal sign. Similar clinical symptoms also have been reported in a 7-year-old boy; however, other patients in the same family presented with spastic paraparesis by their second decade.[sup][4] We propose that the upper motor neurons might be damaged later than peripheral nerves and that the progression is slow.
However, our patient had hyperactive deep tendon reflexes in all extremities and plantar skin reflex responses were extensor MRI examinations performed for investigating the etiology of pyramidal signs were all normal.
(1) The typical clinical manifestation of ADCA type I is cerebellar ataxia with ophthalmoplegia, dementia, extrapyramidal and pyramidal signs. It includes SCA1, SCA3/Machado-Joseph disease (MJD), etc.
The common clinical manifestations of the affected individuals were cerebellar ataxia and pyramidal signs, along with extrapyramidal signs and brainstem or peripheral nerve damage.
Two groups of hands were defined based on the presence or absence of pyramidal signs in the same upper limb.
[sup][10] Two groups of hands were defined, based on the presence or absence of pyramidal signs in the same upper limb.
Common features of this brainstem syndrome are ataxia, dysarthria, hemiparesis and bilateral pyramidal signs usually accompanied by severe headache.
Based on the presence or absence of pyramidal signs in the left upper limb, the ALS patients were divided into two groups: One group with pyramidal signs designated as P group and the other without pyramidal signs designated as NP group.
[sup][14] The patients were divided into two groups according to the presence or absence of pyramidal signs in the left upper limbs.