Nodule of vermis

At a glance

English

Nodule of vermis

Latin (TA2)

Nodulus vermis

System

Brain and spinal cord

Region

Head

Side

Single, on the midline

About the nodule of vermis

The nodule (nodulus) is the most anterior lobule of the inferior vermis, lobule X in the numbered scheme. It is a small rounded knob that hangs into the fourth ventricle's roof, pointing forwards towards the floor of the cavity. Because it is buried between the cerebellum and the brainstem, it is best seen on a midline sagittal cut or after the cerebellum has been lifted away from the pons and medulla. Behind it, across the posterolateral fissure, lies the uvula of the vermis.

From each side of the nodule a thin sheet of white matter, the inferior medullary velum, stretches outwards. It is crescent-shaped: its convex edge merges with the white core of the cerebellum, while its free, concave edge faces the ventricle and is joined to the ependyma and tela choroidea that close the lower roof. Each half of the velum runs laterally as far as the flocculus, and the floccular peduncle on each side ties the flocculus to the nodule. The nodule and both flocculi together make up the flocculonodular lobe, the oldest part of the cerebellum, also called the vestibulocerebellum.

The nodule receives primary vestibular fibres directly from the vestibular nerve, as well as fibres from the vestibular nuclei, and its Purkinje cells project straight back to those nuclei. It is concerned with the position of the head relative to gravity and with how long the vestibulo-ocular reflex goes on after the head stops turning (velocity storage). Through these connections it helps control balance of the trunk and posture, and the coordination of eye movements with head movement.

Damage to the nodule, often in a child by a medulloblastoma growing from the ventricular roof, causes truncal ataxia: the patient sways and staggers when sitting or standing, though limb movements tested lying down may be nearly normal. Positional vertigo and nystagmus, sometimes downbeat or periodic alternating, may appear. A tumour here can also block CSF outflow and cause hydrocephalus.

Function and supply

Function

Part of the vestibulocerebellum, controlling trunk balance and posture and tuning vestibular eye reflexes through its connections with the vestibular nuclei.

Blood supply

Posterior inferior cerebellar artery, through its vermian branches.