Nerve
Lateral corticospinal tract
Descending cortical pathway important for skilled limb movement
High-yield
A lesion above the pyramidal crossing mainly affects the opposite limbs; a lesion of the lateral tract within the cord mainly affects the same side below it. Most fibers cross in the medulla, but the exact proportion and smaller uncrossed pathways vary.
Overview
Corticospinal fibers descend from motor and nearby cortical regions through the internal capsule and brainstem. Most cross in the lower medulla, then continue in the opposite lateral spinal cord. They influence spinal interneurons and motor neurons, especially those involved in precise limb control.
Reference facts
- Origin
- Layer-V cortical projection neurons from primary motor, premotor and nearby sensorimotor regions; giant Betz cells are only one contributing cell type
- Course
- Corona radiata → posterior internal capsule → cerebral peduncle → ventral pons → medullary pyramids → caudal medullary crossing → lateral spinal funiculus
- Motor
- Shapes voluntary movement through spinal interneurons and motor neurons, with an important role in independent distal-limb movements
- Sensory
- It is a descending pathway rather than an ascending sensory route, although corticospinal circuits also help regulate sensory feedback during movement
Clinical correlation
Injury can reduce strength and fine movement, with brisk reflexes, increased tone or an extensor plantar response developing as part of an upper motor neuron syndrome. Acute cord injury may initially cause low tone and reduced reflexes, so early findings can look different.
Frequently asked questions
Where does the lateral corticospinal tract arise?
Layer-V cortical projection neurons from primary motor, premotor and nearby sensorimotor regions; giant Betz cells are only one contributing cell type.
What muscles does the lateral corticospinal tract supply?
Shapes voluntary movement through spinal interneurons and motor neurons, with an important role in independent distal-limb movements.
What is the sensory distribution of the lateral corticospinal tract?
It is a descending pathway rather than an ascending sensory route, although corticospinal circuits also help regulate sensory feedback during movement.
What is the course of the lateral corticospinal tract?
Corona radiata → posterior internal capsule → cerebral peduncle → ventral pons → medullary pyramids → caudal medullary crossing → lateral spinal funiculus.