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Cerebellar falx

The falx cerebelli, also known as the cerebellar falx, is a small vertical dural fold located in the posterior cranial fossa. It partially separates the two cerebellar hemispheres inferiorly and provides structural support to the cerebellum and venous sinuses in this region.

Although much smaller than the falx cerebri, the falx cerebelli has important anatomical and surgical relevance, particularly in posterior fossa pathology, venous sinus evaluation, and midline cerebellar lesions.

Synonyms

  • Falx cerebelli

  • Cerebellar falx

Location

  • Located in the posterior cranial fossa

  • Projects inferiorly from the undersurface of the tentorium cerebelli

  • Occupies the midline between the two cerebellar hemispheres

  • Extends toward the foramen magnum

  • Situated posterior to the vermis and anterior to the occipital bone

  • Closely related to the internal occipital crest

Anatomical components

  • Dural fold:

    • Formed by a double layer of dura mater

    • Thin, sickle-shaped vertical partition

  • Venous component:

    • May contain the occipital sinus along its attached margin

  • Attachment points:

    • Superior attachment to the tentorium cerebelli

    • Inferior attachment to the internal occipital crest

Relations

Anteriorly:

  • Cerebellar vermis

  • Inferior portions of cerebellar hemispheres

Posteriorly:

  • Occipital bone

  • Internal occipital crest

Superiorly:

  • Tentorium cerebelli

Inferiorly:

  • Foramen magnum region

Laterally:

  • Cerebellar hemispheres

Venous associations

  • Occipital sinus:

    • Often located within or along the attached margin of the falx cerebelli

    • Drains into the confluence of sinuses or marginal sinus

  • Marginal sinus (inferiorly):

    • Communicates with vertebral venous plexus

Function

  • Structural support: Provides stabilization and partial separation of cerebellar hemispheres

  • Venous drainage conduit: Supports the occipital sinus when present

  • Dural compartmentalization: Helps organize posterior cranial fossa contents

  • Mechanical protection: Limits excessive displacement of cerebellar tissue

Clinical significance

  • Posterior fossa surgery: Important landmark during midline suboccipital approaches

  • Venous sinus injury: Risk of bleeding if occipital sinus is present within the falx

  • Congenital absence or hypoplasia: Usually incidental and asymptomatic

  • Dural thickening or enhancement: May be seen in inflammatory or neoplastic conditions

  • Mass effect: Displacement can indicate underlying cerebellar or midline posterior fossa lesions

  • Imaging pitfall: Normal falx cerebelli should not be mistaken for pathology

MRI appearance

T1-weighted images:

  • Normal falx cerebelli: Thin, low-signal linear structure

  • Occipital sinus (if present): Flow void or low signal

  • Pathology: Thickening or altered signal in dural disease

T2-weighted images:

  • Normal: Low-signal intensity dural fold

  • Venous sinus: Flow void if patent

  • Pathology: Loss of flow void or abnormal signal suggests thrombosis or infiltration

FLAIR:

  • Normal: Hypointense thin line against cerebellar tissue

  • Pathology: Hyperintensity in dural inflammation or venous thrombosis

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

  • Pathology: Restricted diffusion may be seen in dural empyema or venous thrombosis

Post-contrast T1-weighted images:

  • Normal: Thin linear dural enhancement

  • Occipital sinus: Enhances if patent

  • Pathology: Thick, nodular, or asymmetric enhancement in meningioma, metastasis, or inflammation

CT appearance

Non-contrast CT:

  • Normal falx cerebelli: Thin linear hyperdense dural structure

  • Occipital sinus: Usually not well visualized unless calcified or thrombosed

  • Bone landmark: Seen adjacent to the internal occipital crest

Post-contrast CT:

  • Normal: Thin enhancing dural fold

  • Venous sinus: Enhancing occipital sinus when present

  • Pathology: Thickening or abnormal enhancement in dural-based disease

MRI images

mri Cerebellar falx (falx cerebelli) axial anatomy image -img-00000-00000

MRI images

mri Cerebellar falx (falx cerebelli) coronal anatomy image -img-00000-00000