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Vein of cerebellomedullary cistern

The vein of the cerebellomedullary cistern is a posterior fossa venous structure situated within the cerebellomedullary cistern (cisterna magna), the largest subarachnoid cistern at the inferior aspect of the posterior cranial fossa. It courses along the dorsal surface of the medulla and inferior cerebellum, draining venous blood from the inferior cerebellar hemispheres, cerebellar tonsils, and dorsal medulla.

This vein communicates with adjacent posterior fossa venous structures, including the vein of the great horizontal fissure, inferior vermian vein, and bridging veins draining into the transverse and sigmoid sinuses. It plays an important role in venous outflow of the cerebellum and medulla, and its anatomy is relevant in posterior fossa surgery, vascular malformation assessment, and posterior circulation imaging.

Synonyms

  • Cerebellomedullary vein

  • Vein of the cisterna magna

  • Posterior fossa bridging vein

Function

  • Drains venous blood from the inferior cerebellum (tonsils, hemispheres) and dorsal medulla

  • Provides venous communication between deep cerebellar and dural venous sinuses

  • Contributes to venous outflow of the posterior cranial fossa

  • Acts as a landmark in posterior fossa microsurgery and vascular procedures

MRI Appearance

T1-weighted images (non-contrast):

  • Vein appears as a linear hypointense flow void within the CSF of the cerebellomedullary cistern

  • Surrounded by hyperintense CSF, which provides contrast

T2-weighted images:

  • Also seen as a flow void (signal loss) against the bright CSF background

  • Useful for anatomical localization of venous structures

MRA (Magnetic Resonance Angiography):

  • Conventional MRA is arterial-focused and less reliable for venous depiction

  • Dedicated MR Venography (MRV) is preferred

MRV (Magnetic Resonance Venography):

  • Demonstrates the vein as a linear enhancing venous channel draining the posterior fossa

  • Contrast-enhanced MRV provides the most reliable depiction of venous anatomy, stenosis, or thrombosis

  • Useful in evaluating posterior fossa venous malformations or venous sinus variations

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Vein enhances strongly, appearing as a linear enhancing structure against CSF

  • Helpful in detecting venous anomalies, thrombosis, or collaterals

CT Appearance

Non-contrast CT:

  • Vein itself is not well visualized; cistern is hypodense due to CSF

  • Acute thrombosis may appear as a hyperdense linear structure within the cistern

CTV (CT Venography):

  • Clearly depicts the vein of the cerebellomedullary cistern filled with contrast

  • Demonstrates its connections with adjacent posterior fossa veins and dural venous sinuses

  • Useful for detecting venous thrombosis, anomalies, or displacement by mass lesions

MRI images

Vein of cerebellomedullary cistern