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Cerebellar tentorium

The cerebellar tentorium, or tentorium cerebelli, is a crescent-shaped fold of dura mater that forms a crucial anatomical barrier within the cranial cavity. It separates the cerebellum, which lies below, from the inferior portion of the occipital lobes of the cerebral hemispheres above. This dural fold plays a vital role in supporting and protecting the brain by partitioning the cranial vault into supratentorial and infratentorial compartments. It is attached along the margins of the posterior cranial fossa and is pivotal in several clinical scenarios, such as brain herniations.

Synonyms

  • Tentorium cerebelli

  • Cerebellar tentorium

  • Tentorial membrane

Anatomy

  • A strong, horizontal dural fold situated in the posterior cranial fossa.

  • Attached:

    • Anteriorly to the clinoid processes of the sphenoid bone.

    • Laterally to the superior border of the petrous part of the temporal bone.

    • Posteriorly to the grooves for the transverse sinuses on the occipital bone.

  • Contains a central opening (tentorial notch or incisura) through which the brainstem passes.

  • Forms a “roof” over the cerebellum and a “floor” for the occipital lobes.

Arterial Supply

  • Mainly supplied by meningeal branches of the following arteries:

    • Occipital artery (branch of the external carotid)

    • Middle meningeal artery (branch of the maxillary artery, itself a branch of the external carotid)

    • Ascending pharyngeal artery

    • Small branches from the vertebral artery and posterior meningeal arteries

Venous Drainage

  • The tentorium contains major venous sinuses:

    • Transverse sinuses

    • Straight sinus

    • Superior petrosal sinuses

  • These sinuses receive blood from cerebral and cerebellar veins and drain ultimately into the internal jugular veins.

Function

  • Physically separates the cerebrum from the cerebellum.

  • Supports and stabilizes the occipital lobes.

  • Prevents downward displacement of the cerebral hemispheres.

  • Involved in compartmentalizing the cranial cavity, which is clinically significant in the context of brain herniation syndromes (e.g., transtentorial herniation).

MRI Appearance

  • Appears as a thin, hypointense (dark) line on T1- and T2-weighted images due to its dense fibrous tissue.

  • Best visualized in sagittal and coronal planes, outlining the tentorial “roof.”

  • Enhanced with gadolinium contrast due to the presence of dura, but generally remains hypointense relative to brain tissue.

  • Acts as an important landmark in evaluating mass effect, brain herniations, and dural-based lesions (e.g., meningiomas).

CT Appearance

  • Seen as a linear, iso to hyperintense structure within the posterior cranial fossa.

  • Best appreciated on non-contrast CT as a sharply-defined line separating cerebellum from occipital lobes.

  • Can sometimes be obscured by adjacent bone, but may be highlighted in cases of calcification or hemorrhage.

  • Important for identifying mass effect, midline shift, or hemorrhagic collections near the tentorium (e.g., subdural hematoma).

MRI images

Cerebellar tentorium MRI 3T coronal image

MRI images

Cerebellar tentorium MRI 3T sagittal image

CT image

Cerebellar tentorium ct