Tuber of vermis

At a glance

English

Tuber of vermis

Latin (TA2)

Tuber vermis

System

Brain and spinal cord

Region

Head

Side

Single, on the midline

About the tuber of vermis

The tuber (Latin for a swelling) is a lobule of the vermis, the narrow midline part of the cerebellum that joins the two hemispheres. It lies on the posterior and inferior aspect of the vermis, just below the horizontal fissure, and is the rearmost division of the inferior vermis. In the numbered scheme of cerebellar lobules it is lobule VIIB, sharing lobule VII with the folium above it, and it belongs to the posterior lobe.

It is a small lobule in the midline, but it does not stand alone. On each side its folia run straight on into the hemisphere, where they broaden out into the big inferior semilunar lobules (crus II of the ansiform lobule in the modern scheme). These lobules make up a large share of the lower surface of each cerebellar hemisphere, so the tuber acts as the narrow midline bridge between two broad hemispheric territories. Above the tuber, across the horizontal fissure, lies the folium of the vermis; below and in front, the prepyramidal fissure separates it from the pyramid of the vermis, which leads on to the uvula and nodule.

The tuber and folium together form part of the oculomotor vermis, a region of the posterior vermis that adjusts the size and accuracy of saccadic eye movements and helps smooth pursuit. They receive mossy fibres relayed through the pontine nuclei from cerebral cortex, and their Purkinje cells project to the fastigial nucleus, which in turn acts on brainstem centres for gaze.

Lesions of the posterior vermis in this region, from midline tumours, infarcts or degeneration, can make saccades overshoot or undershoot their targets (ocular dysmetria) and break up smooth tracking. Because the vermis also controls the trunk, damage spreading to neighbouring lobules adds an unsteady, broad-based gait. The tuber is a recognised landmark on midline sagittal MRI of the posterior fossa.

Function and supply

Function

Part of the posterior vermis linked with the oculomotor vermis, helping calibrate saccades and smooth pursuit through the fastigial nucleus.

Blood supply

Vermian branches of the posterior inferior and superior cerebellar arteries.