Lateral reticulospinal tract

At a glance

English

Lateral reticulospinal tract

Latin (TA2)

Tractus reticulospinalis lateralis

System

Nerve

Region

Whole body

Side

Single, on the midline

About the lateral reticulospinal tract

The lateral reticulospinal tract, also known as the medullary reticulospinal tract, is one of two pathways by which the reticular formation of the brainstem acts on the spinal cord. Its partner, the medial reticulospinal tract, comes from the pons. The reticular formation itself is a loose network of nuclei with indistinct borders running through the core of the brainstem; its medial cell columns are the source of most descending fibres.

The lateral tract arises from the gigantocellular reticular nucleus and nearby cell groups of the medulla oblongata. Its fibres descend on both sides, with a larger share on the same side, and occupy the anterior part of the lateral funiculus, close to the lateral horn and the lateral spinothalamic fibres. They run the length of the cord and end mainly on interneurons of the intermediate grey matter, which in turn act on motor neurons of the trunk and proximal limbs. Some fibres also reach the preganglionic autonomic neurons of the lateral horn.

Grouped by origin and target, the descending motor pathways form two groups. The reticulospinal and vestibulospinal tracts form the medial system, which keeps the body upright and steady; the corticospinal and rubrospinal tracts form the lateral system, responsible for fine and skilled limb movement. The two systems work together, so even a delicate hand task rests on a stable posture provided by the medial pathways. The medullary tract tends to inhibit extensor tone and to ease flexor activity, opposing the pontine tract; it also helps generate the rhythm of walking and contributes to the control of breathing and of blood pressure.

The tract receives strong input from the motor cortex, so cortical lesions remove its drive. The resulting imbalance between the two reticulospinal pathways is one reason for the raised extensor tone and spasticity seen after a stroke or spinal cord injury.

Course and supply

Supplies

Acts on interneurons and motor neurons of the trunk and proximal limbs, mainly damping extensor tone, and helps control posture, walking rhythm and some autonomic functions.

Blood supply

Runs in the lateral funiculus, supplied by the anterior spinal artery and the arterial vasocorona.