Fourth ventricle

What it is

The fourth ventricle is a fluid-filled cavity located between the brainstem and the cerebellum, part of the brain's ventricular system. Cerebrospinal fluid flows through it on its way out to the spaces around the brain and spinal cord. It can be displaced or distorted in severe Chiari malformations.

Understanding Fourth ventricle

CSF travels from the upper ventricles through the cerebral aqueduct into the fourth ventricle, then exits through its outlets (the foramina of Luschka and Magendie) into the subarachnoid space. In Chiari malformation type II, the fourth ventricle can be elongated and displaced downward through the foramen magnum along with the brainstem. This distortion can affect CSF flow and is part of the complex anatomy of type II. In some surgeries for severe Chiari, attention to the fourth ventricle's outlets may be part of restoring CSF flow. Understanding the fourth ventricle helps clarify how CSF moves in this region and how its displacement contributes to severe Chiari anatomy.

Why it matters

Understanding the fourth ventricle helps families see how CSF flows through the brainstem region and how its displacement in severe Chiari contributes to the abnormal anatomy and CSF flow problems.