Lateral vestibulospinal tract

At a glance

English

Lateral vestibulospinal tract

Latin (TA2)

Tractus vestibulospinalis lateralis

System

Nerve

Region

Whole body

Side

Single, on the midline

About the lateral vestibulospinal tract

The lateral vestibulospinal tract is the larger of the two vestibulospinal pathways and part of the medial descending system that governs balance and posture. Its fibres arise mostly from the lateral vestibular nucleus, or nucleus of Deiters, in the floor of the fourth ventricle at the junction of pons and medulla. Smaller numbers come from the superior and inferior vestibular nuclei. The giant cells of Deiters' nucleus are laid out in body order, so different parts project to cervical, thoracic or lumbosacral levels.

The tract descends on the same side without crossing. In the cord it runs in the anterior part of the white matter, at the border of the anterior and lateral funiculi, and it extends all the way to the lumbar and sacral segments. Its fibres end on interneurons of the medial intermediate grey and directly on motor neurons of the anterior horn.

Its effect is to excite motor neurons of the extensor, antigravity muscles of the limbs and the muscles of the trunk, while inhibiting flexors through interneurons. When the head tilts or the body starts to fall, signals from the utricle, saccule and semicircular canals reach the vestibular nuclei and the tract quickly raises extensor tone on the side towards which the body leans. This keeps the legs straight under load and the body upright.

The lateral vestibular nucleus is itself controlled by the cerebellum, mainly through Purkinje cells of the flocculonodular lobe and the vermis, which inhibit it and fine-tune postural adjustments. If the brainstem is cut between the vestibular nuclei and the red nucleus, the loss of higher control leaves this tract acting unopposed, and the limbs become rigidly extended.

Course and supply

Supplies

Excites extensor motor neurons of the limbs and trunk on the same side, maintaining upright posture and balance in response to vestibular signals.

Blood supply

Runs in the anterior and lateral funiculi, supplied by the anterior spinal artery.