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Cerebral falx

The cerebral falx, also known as the falx cerebri, is a strong, sickle-shaped vertical fold of dura mater that descends in the midline between the two cerebral hemispheres. It provides mechanical support to the brain, limits excessive hemispheric movement, and contains major venous sinuses essential for cerebral venous drainage.

The falx cerebri is of major importance in neuroimaging, neurosurgery, trauma, venous sinus disease, and intracranial mass effect assessment.

Synonyms

  • Falx cerebri

  • Interhemispheric dural fold

Location

  • Situated in the midline of the cranial cavity

  • Extends within the longitudinal cerebral fissure

  • Separates the right and left cerebral hemispheres

  • Anterior attachment to the crista galli of the ethmoid bone

  • Posterior attachment to the internal occipital protuberance

  • Inferior free margin overlies the corpus callosum

  • Superior margin attaches to the inner table of the skull

Anatomical components

  • Dural layers:

    • Composed of two layers of meningeal dura mater

  • Superior margin:

    • Contains the superior sagittal sinus

  • Inferior free margin:

    • Contains the inferior sagittal sinus

  • Posterior attachment:

    • Joins the tentorium cerebelli

    • Forms the straight sinus at the junction

Relations

Superiorly:

  • Inner table of frontal, parietal, and occipital bones

  • Superior sagittal sinus

Inferiorly:

  • Corpus callosum

  • Pericallosal cistern

Anteriorly:

  • Crista galli of the ethmoid bone

Posteriorly:

  • Tentorium cerebelli

  • Straight sinus

  • Internal occipital protuberance

Laterally:

  • Medial surfaces of the cerebral hemispheres

Venous sinuses related to the falx

  • Superior sagittal sinus:

    • Runs along the convex superior border

  • Inferior sagittal sinus:

    • Runs within the inferior free margin

  • Straight sinus:

    • Formed at the junction of falx cerebri and tentorium cerebelli

Function

  • Structural support: Stabilizes cerebral hemispheres within the cranial vault

  • Limitation of brain displacement: Reduces lateral brain shift during acceleration or trauma

  • Venous drainage: Houses major dural venous sinuses

  • Compartmentalization: Divides supratentorial intracranial space into right and left compartments

Clinical significance

  • Subfalcine herniation: Cingulate gyrus herniates beneath the falx due to mass effect

  • Falcine meningioma: Common site for dural-based tumors

  • Trauma: Falx acts as a pivot point for shear injury

  • Venous sinus thrombosis: Involvement of superior or inferior sagittal sinus

  • Calcification: Common physiological calcification, especially with aging

  • Surgical landmark: Important reference in interhemispheric surgical approaches

MRI appearance

T1-weighted images:

  • Normal falx: Low signal intensity, similar to dura

  • Venous sinuses: Flow voids within superior and inferior sagittal sinuses

T2-weighted images:

  • Normal falx: Low signal intensity

FLAIR:

  • Normal: Low-signal linear structure in the midline

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

Post-contrast T1-weighted images:

  • Normal falx: Thin linear enhancement due to dural vascularity

  • Meningioma: Intense homogeneous enhancement with possible dural tail

CT appearance

Non-contrast CT:

  • Normal falx: Thin hyperdense midline structure

Post-contrast CT:

  • Normal: Mild linear enhancement

  • Meningioma: Dense, homogeneous enhancement

MRI images

MRI Cerebral falx axial anatomy image -img-00000-00000_00001

MRI images

MRI Cerebral falx coronal anatomy image -img-00000-00000