Anatomy and Physiology of the Vestibulospinal System

Abstract

　Descending information from the labyrinth to the spinal motoneurons is mainly conveyed through the vestibulospinal system, which consists of the lateral and medial vestibulospinal tracts. The lateral vestibulospinal tract (LVST) arises mainly from the lateral vestibular nucleus and descends ipsilaterally in the ventrolateral funiculus. It mainly receives input from the otolith organs, extends throughout the length of the spinal cord, and exerts excitation on the extensor muscles of the lower leg. Single LVST axons have multiple axon collaterals at different segments along the entire length of the spinal cord, thus playing an important role in maintaining the posture. In contrast, the medial vestibulospinal tract (MVST) originates in the descending, medial and lateral vestibular nuclei, and descends bilaterally in the ventromedial funiculus of the cervical cord. It conveys mainly semicircular canal inputs to the neck motoneurons, and single MVST axons have multiple axon collaterals terminating on neck motoneurons in different segments of the cervical spinal cord, thus playing an important role in the vestibulocollic reflex.