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Cerebellopontine cistern

The cerebellopontine (CP) cistern is a CSF-filled subarachnoid space located in the posterolateral aspect of the pontine region at the junction of the cerebellum and pons. It lies between the cerebellar flocculus, middle cerebellar peduncle, and lateral aspect of the pons, extending laterally to the internal auditory canal. This cistern is an important conduit for cerebrospinal fluid (CSF) and serves as a neurovascular corridor, containing cranial nerves VII (facial) and VIII (vestibulocochlear), the anterior inferior cerebellar artery (AICA), and veins of the posterior fossa.

The CP cistern is clinically significant because it is a common site for acoustic neuromas, vestibular schwannomas, epidermoid cysts, and arachnoid cysts. Its anatomical relationships with the brainstem, cerebellum, and cranial nerves make it crucial for neurosurgical planning and radiological assessment.

Function

  • Serves as a CSF reservoir, allowing circulation around the posterior fossa

  • Provides a protective cushion for cranial nerves VII and VIII

  • Acts as a neurovascular corridor for arteries and veins of the posterior fossa

  • Facilitates cranial nerve function and posterior fossa homeostasis

  • Guides surgical approaches for CPA lesions, tumors, and vascular malformations

Synonyms

  • CPA cistern

  • Cerebellopontine angle cistern

  • Posterolateral pontocerebellar cistern

MRI Appearance

T1-weighted images:

  • CSF in the CP cistern appears low signal intensity (hypointense)

  • Cranial nerves VII and VIII may be visualized as tiny intermediate signal structures within the cistern

  • Lesions such as schwannomas or epidermoid cysts alter the signal, appearing isointense to hypointense relative to CSF

T2-weighted images:

  • CSF appears high signal intensity (hyperintense)

  • Cranial nerves appear as low-to-intermediate signal linear structures coursing through the hyperintense CSF

  • Pathology like cysts or tumors appears as low to intermediate signal, distinguishable from CSF

STIR (Short Tau Inversion Recovery):

  • CSF remains hyperintense, and edema or inflammation of surrounding tissue appears bright

  • Useful for identifying tumor-associated edema or inflammatory changes

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal cistern shows no enhancement, cranial nerves are minimally enhanced only if vascularized

  • Pathological lesions such as schwannomas, meningiomas, or metastases demonstrate marked enhancement, helping define lesion extent and relation to cranial nerves

CT Appearance:

  • CSF in the cistern appears as hypodense (dark) relative to brain parenchyma

  • Cranial nerves are generally not visualized unless enlarged or involved by pathology

  • CT clearly delineates bony margins of the internal auditory canal, posterior fossa, and CPA recess

  • Useful for evaluating bony erosions, calcifications, and mass effect on adjacent structures

MRI images

Cerebellopontine cistern mri axial image -img-00000-00000

MRI images

Cerebellopontine cistern mri axial image