Corticospinal tract
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Anatomy
CST is a collection of axons that carry movement-related information from the cerebral cortex to the spinal cord.
- It starts at Primary motor cortex / Premotor areas and terminates on LMN / Spinal cord Interneurons.
- The neurons that travel in CST are referred to as UMN and synapse on neurons in the spinal cord called LMN, which make contact with skeletal muscle to cause muscle contraction.
- CST is one of the major pathways for carrying movement-related information from the brain to the spinal cord and has approximately 1 million nerve fibres
- It involved in a variety of movements, including behaviors like walking and reaching, but it is especially important for fine finger movements e.g. writing, typing, or buttoning clothes.
- Approximately 90% of the fibers in CST decussate, or cross over to the other side of the brainstem.They form the lateral corticospinal tract
- The other 10% of the corticospinal tract fibers will not decussate; they will continue down into the ipsilateral spinal cord. They are known as the anterior (or ventral) corticospinal tract.
- Lateral corticospinal tract primarily controls the movement of muscles in the limbs
- Anterior corticospinal tract is involved with movement of the muscles of the trunk, neck, and shoulders.
Clinic
When UMN of the corticospinal tract are damaged, it can lead to a collection of deficits sometimes called UMN syndrome.
- A lesion of the CST cranial to the decussation of the pyramids will result in deficits on the contralateral side.
- A lesion of the CST caudal to the decussation of the pyramids will result in deficits on the ipsilateral side.