Topics

Topic

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Corticospinal tract

The corticospinal tract is a major descending white matter pathway essential for voluntary motor control, particularly of the limbs. Originating from the motor cortex, its fibers travel through the internal capsule, brainstem, and into the spinal cord, ultimately synapsing on lower motor neurons. Precise imaging assessment of this tract is crucial in evaluating neurological diseases such as stroke, multiple sclerosis, or traumatic injury.

Function

  • Responsible for voluntary and skilled motor activity, especially fine movements of distal extremities (hands, fingers).

  • Involved in rapid, precise movement and motor learning.

  • Lesions in this tract cause upper motor neuron signs, including spasticity, hyperreflexia, and weakness.

MRI Appearance

T1-Weighted MRI

  • Normal white matter, including the corticospinal tract, is hyperintense (bright) compared to gray matter.

  • The tract itself is not directly visualized—it merges with other white matter pathways.

  • Pathological involvement (e.g., infarct, demyelination) appears hypointense (dark) compared to normal white matter.

T2-Weighted MRI

  • Normal white matter, including the corticospinal tract, is hypointense (dark) relative to cortical gray matter.

  • The tract is not individually distinguished unless involved by pathology.

  • Pathological changes (such as infarct, demyelination) appear as hyperintense (bright) signals along the expected tract location.

FLAIR MRI

  • White matter, including the corticospinal tract, is hypointense to isointense (dark or similar) relative to gray matter.

  • The normal tract is not visualized specifically—it is visible only when affected by pathology.

  • Abnormalities (e.g., demyelination, edema, infarction) are hyperintense (bright) along the tract’s course.

CT Appearance

  • White matter, including the corticospinal tract, is hypodense (darker) than gray matter.

  • The tract itself is not directly visualized on standard CT.

  • Acute pathology (e.g., infarction) involving the tract may cause focal hypodensity (dark area) along expected regions such as the posterior limb of the internal capsule.

  • Chronic damage may show as atrophy or loss of volume in affected areas.

MRI images

Corticospinal trac mri 3t axial image