Anatomy: Posterior Fossa, Hindbrain & Craniocervical Junction

Cerebellar vermis

The cerebellar vermis is the midline part of the cerebellum, which can be displaced downward in more severe Chiari malformations.

In short: Cerebellar vermis

It is the midline strip connecting the two cerebellar hemispheres.
It contributes to balance and coordination of the trunk.
It can be displaced downward in Chiari type II.
Its position helps characterize the malformation.

What it is

The cerebellar vermis is the narrow, midline portion of the cerebellum that connects its two hemispheres. It contributes to balance and the coordination of the trunk and is among the structures that can be displaced downward in more severe Chiari malformations.

Understanding Cerebellar vermis

Sitting in the midline between the cerebellar hemispheres, the vermis helps coordinate posture, gait, and trunk movements. In Chiari malformation type II, downward displacement can involve the vermis along with other hindbrain structures through the foramen magnum, contributing to the more complex anatomy of that type. (In the unrelated Dandy-Walker malformation, the vermis is underdeveloped — a different condition.) The vermis's position and involvement help characterize the malformation, particularly in the more severe types. Understanding the vermis adds detail to the picture of which cerebellar structures are affected in Chiari, especially type II, where more of the cerebellum is involved than in type I.

Why it matters

Understanding the cerebellar vermis helps families see which midline cerebellar structure can be involved in more severe Chiari malformations, adding detail to the anatomy of type II.

Common questions

What is the cerebellar vermis?

The midline strip connecting the two cerebellar hemispheres.

What does it do?

It contributes to balance and coordination of the trunk.

How is it involved in Chiari?

It can be displaced downward in type II.

Bottom line

The cerebellar vermis is the midline part of the cerebellum that can be displaced downward in more severe Chiari malformations, such as type II.

More terms in Anatomy: Posterior Fossa, Hindbrain & Craniocervical Junction

Cerebellar hemispheresThe cerebellar hemispheres are the two large lobes of the cerebellum that coordinate movement of the limbs.
BrainstemThe brainstem is the lower part of the brain that controls vital functions and connects the brain to the spinal cord, displaced downward in more severe Chiari types.
Medulla oblongataThe medulla oblongata is the lowest part of the brainstem, controlling breathing and heart rate, and can be displaced in severe Chiari malformations.
PonsThe pons is the middle part of the brainstem, relaying signals and contributing to functions that can be affected in severe Chiari malformations.
MidbrainThe midbrain is the upper part of the brainstem, involved in eye movement and other functions, generally less directly affected in Chiari malformation.

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