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Prepontine cistern

The prepontine cistern is a subarachnoid cistern located in front of the pons, containing cerebrospinal fluid (CSF) and important neurovascular structures. It is one of the basal cisterns of the brain, playing a role in CSF circulation around the brainstem. The cistern is clinically significant as it is a common site for aneurysms, tumors (such as epidermoid cysts), inflammatory conditions, and traumatic hemorrhage.

Synonyms

  • Pontine cistern (anterior)

  • Basal cistern anterior to pons

  • Prepontine subarachnoid cistern

Boundaries

  • Anteriorly: Clivus and dorsum sellae (posterior sphenoid bone)

  • Posteriorly: Pons

  • Superiorly: Interpeduncular cistern

  • Inferiorly: Medullary cistern and foramen magnum

  • Laterally: Cerebellopontine cisterns

Contents

  • Cranial nerves: Abducens nerve (CN VI) traverses the cistern

  • Vessels:

    • Basilar artery and its branches

    • Perforating arteries to the brainstem

  • CSF: Free flow of cerebrospinal fluid around the ventral brainstem

Function

  • Acts as a CSF reservoir and pathway in front of the pons

  • Protects and cushions brainstem and vascular structures

  • Provides space for cranial nerve passage and vascular circulation

Clinical Significance

  • Aneurysms: Basilar artery and its branches may form aneurysms here

  • Tumors: Epidermoid cysts, meningiomas, and schwannomas may involve this cistern

  • Hemorrhage: Subarachnoid hemorrhage may accumulate within the cistern

  • Inflammation/Infection: Meningitis may cause abnormal signal or enhancement

  • Trauma: Prepontine cistern effacement may be an early sign of raised intracranial pressure or mass effect

MRI Appearance

T1-weighted images:

  • CSF in cistern appears very dark (low signal intensity)

  • Cranial nerves and vessels appear as intermediate to low signal structures

  • Pathology (tumor, hemorrhage) may appear as intermediate to high signal depending on content

T2-weighted images:

  • CSF appears very bright (high signal intensity)

  • Cranial nerves and vessels: dark/flow voids within bright CSF background

  • Lesions (tumor, epidermoid, cysts): variable intensity compared to CSF

FLAIR (Fluid-Attenuated Inversion Recovery):

  • CSF signal is suppressed (dark)

  • Pathological contents (blood, pus, proteinaceous material, tumor) appear bright

  • Useful for detecting meningitis, hemorrhage, or neoplastic infiltration in the cistern

CT Appearance

Non-Contrast CT:

  • CSF in cistern appears as low attenuation (dark)

  • Cranial nerves/vessels not directly visible without contrast

  • Acute hemorrhage: appears as hyperdense material within cistern

  • Mass lesions: cause cisternal effacement or focal hyper/hypodensity

Post-Contrast CT:

  • Normal CSF in cistern does not enhance

  • Vessels enhance brightly, outlining the cistern

  • Pathology:

    • Tumors (meningioma, metastasis) show enhancing masses

    • Inflammation or infection may cause abnormal cisternal enhancement

    • Abscess or cyst: may show rim enhancement with central low attenuation

MRI images

Prepontine cistern mri 3t sagittal image

CT image

Prepontine cistern CT sag anatomy image -img-00001-00001