corticospinale

The corticospinal tract, also known as the pyramidal tract, is a major motor pathway that originates in the cerebral cortex and descends to the spinal cord. It plays a crucial role in voluntary movement, particularly fine motor control of the limbs and trunk. The tract is composed of two main divisions: the lateral corticospinal tract and the anterior corticospinal tract. The lateral corticospinal tract contains about 90% of the axons and is primarily responsible for controlling distal limb muscles, enabling precise movements like finger manipulation. The anterior corticospinal tract, carrying the remaining axons, influences axial and proximal muscles involved in posture and gross movements.

Neurons in the motor cortex, premotor cortex, and supplementary motor area give rise to the corticospinal fibers. These fibers descend through the internal capsule, a white matter structure in the brain, and then pass through the brainstem. In the medulla oblongata, the majority of the fibers (about 75-90%) decussate, or cross over, to the opposite side of the body, forming the lateral corticospinal tract. The remaining uncrossed fibers continue down the spinal cord as the anterior corticospinal tract. Upon reaching their target levels in the spinal cord, the corticospinal axons synapse with motor neurons and interneurons in the ventral horn, thereby influencing muscle activity. Damage to the corticospinal tract can result in various motor deficits, including weakness, paralysis, spasticity, and impaired fine motor skills.