Cerebellomedullary cistern

The cerebellomedullary cistern, also known as the cisterna magna, is one of the largest subarachnoid cisterns in the central nervous system. It is located between the cerebellum and the medulla oblongata and plays a crucial role in the circulation of cerebrospinal fluid (CSF).

Anatomy

The cerebellomedullary cistern is situated in the posterior cranial fossa. It is bordered superiorly by the inferior surface of the cerebellum, inferiorly by the dorsal surface of the medulla oblongata, and laterally by the cerebellar hemispheres. The cistern is continuous with the fourth ventricle via the foramen of Magendie, allowing for the flow of CSF from the ventricular system into the subarachnoid space.

Boundaries

• Superiorly: Inferior surface of the cerebellum
• Inferiorly: Dorsal surface of the medulla oblongata
• Laterally: Cerebellar hemispheres

Function

The primary function of the cerebellomedullary cistern is to facilitate the circulation of cerebrospinal fluid within the subarachnoid space. It acts as a reservoir for CSF, which cushions the brain and spinal cord, providing mechanical protection and maintaining homeostasis within the central nervous system.

Clinical Significance

The cerebellomedullary cistern is of clinical importance in several medical conditions and procedures:

Hydrocephalus

In conditions such as hydrocephalus, where there is an abnormal accumulation of CSF, the cerebellomedullary cistern may become enlarged. This can be detected through imaging techniques such as MRI or CT scan.

Chiari Malformation

In Chiari malformation, the cerebellar tonsils may herniate through the foramen magnum into the cerebellomedullary cistern, leading to compression of the brainstem and disruption of CSF flow.

Lumbar Puncture

The cerebellomedullary cistern is sometimes accessed during a lumbar puncture to obtain CSF for diagnostic purposes, although this is more commonly done at the lumbar level.

Imaging

The cerebellomedullary cistern can be visualized using various imaging modalities:

• Magnetic Resonance Imaging (MRI): Provides detailed images of the cistern and surrounding structures, useful in diagnosing conditions like Chiari malformation.
• Computed Tomography (CT): Can be used to assess the size and shape of the cistern, particularly in cases of trauma or hydrocephalus.

Surgical Considerations

In certain neurosurgical procedures, the cerebellomedullary cistern may be accessed to relieve pressure or to perform a cisternostomy. This requires careful navigation to avoid damage to the surrounding neural structures.

See Also

• Subarachnoid space
• Cerebrospinal fluid
• Fourth ventricle
• Chiari malformation

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