Anatomy: Posterior Fossa, Hindbrain & Craniocervical Junction
Midbrain
The midbrain is the upper part of the brainstem, involved in eye movement and other functions, generally less directly affected in Chiari malformation.
In short: Midbrain
- It is the upper part of the brainstem.
- It is involved in eye movement, hearing, and alertness.
- It is generally less directly affected than lower brainstem structures.
- It is part of the brainstem connecting the cerebrum to lower structures.
What it is
The midbrain is the upper part of the brainstem, located above the pons and connecting to the cerebrum. It is involved in functions such as eye movement, certain reflexes, hearing, and aspects of alertness. It is generally less directly affected in Chiari malformation than the lower brainstem.
Understanding Midbrain
As the topmost part of the brainstem, the midbrain sits higher than the structures (medulla, obex) most involved in Chiari herniation. Its functions include controlling eye movements and pupillary responses, relaying auditory and visual information, and contributing to alertness. While the lower brainstem (medulla and pons) is what descends in severe Chiari, the midbrain can be relevant to certain associated findings — for example, some eye-movement abnormalities relate to upper brainstem function, and conditions affecting CSF and pressure can involve this region. Understanding the midbrain completes the picture of the brainstem's three parts, clarifying that Chiari herniation primarily involves the lower brainstem rather than the midbrain.
Why it matters
Understanding the midbrain helps families see the full structure of the brainstem and recognize that Chiari herniation primarily involves the lower brainstem, with the midbrain less directly affected.
Common questions
What is the midbrain?
The upper part of the brainstem.
What does it do?
It is involved in eye movement, hearing, reflexes, and alertness.
Is it directly affected in Chiari?
Generally less so than the lower brainstem structures.
Bottom line
The midbrain is the upper brainstem, involved in eye movement and other functions, and generally less directly affected in Chiari than lower structures.
Browse all 265 Chiari malformation definitions
Read the Chiari malformation patient guides
Not sure which page you need? Put words to it with the symptom navigator