Vestibular nuclei

At a glance

English

Vestibular nuclei

Latin (TA2)

Nuclei vestibulares

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the vestibular nuclei

The vestibular nuclei are the brainstem cell groups in which the vestibular part of the vestibulocochlear nerve (cranial nerve VIII) ends. They occupy a large area beneath the outer part of the fourth ventricle's floor, the vestibular area of the rhomboid fossa, and extend from the lower pons down into the medulla oblongata. On each side there are four main nuclei: superior, lateral, medial and inferior (also called the spinal or descending nucleus). The medial nucleus lies closest to the floor and the midline; the lateral nucleus, with its very large cells (Deiters' cells), lies further out and deeper.

The vestibular nerve enters the brainstem at the pontomedullary junction, medial to the cochlear fibres, and passes inwards between the inferior cerebellar peduncle and the trigeminal nerve's spinal tract. Its fibres then split into ascending branches, which end mostly in the superior and lateral nuclei, and descending branches, which end in the medial and inferior nuclei. Some primary fibres bypass the nuclei and go straight to the cerebellum, mainly the flocculonodular lobe. The nuclei also receive heavily from the cerebellum itself, including Purkinje cell axons from the flocculus and nodule, and from the spinal cord, the visual system and the opposite vestibular nuclei.

Their output goes to three main destinations. Fibres rise through the medial longitudinal fasciculus to reach the nuclei of the oculomotor, trochlear and abducens nerves, providing the vestibulo-ocular reflex that keeps the eyes fixed on a target while the head moves. Fibres descend to the spinal cord: the lateral vestibulospinal tract, from the lateral nucleus, excites antigravity muscles of the limbs, while the medial vestibulospinal tract, mainly from the medial nucleus, steadies the head and neck. Further fibres go to the cerebellum, the reticular formation and, through the thalamus, to the cortex, giving conscious awareness of head movement and position.

Damage to the vestibular nuclei, for example from a stroke in the lateral medulla or a demyelinating plaque, causes vertigo, nausea and vomiting, nystagmus and a tendency to fall to one side. Overactivity of the lateral nucleus, when released from higher control, contributes to the extended limb posture of decerebrate rigidity. The nuclei are also involved in motion sickness.

Function and supply

Function

Receive head-movement and position signals from the inner ear and use them to stabilise gaze (vestibulo-ocular reflex), maintain posture and balance (vestibulospinal tracts) and inform the cerebellum and cortex.

Blood supply

Branches of the anterior inferior cerebellar artery and the posterior inferior cerebellar artery, with small branches of the vertebral and basilar arteries.