Falx cerebri

At a glance

English

Falx cerebri

Latin (TA2)

Falx cerebri

System

Brain and spinal cord

Region

Head

Side

Single, on the midline

About the falx cerebri

The falx cerebri is one of the folds of the inner, meningeal layer of the dura mater that partition the cranial cavity. It is shaped like a sickle (falx in Latin): narrow at the front, broader behind, with a convex upper edge fixed to the skull and a free, concave lower edge. It drops vertically into the longitudinal fissure, so that it lies between the medial surfaces of the right and left cerebral hemispheres.

Its narrow front end is anchored to the crista galli of the ethmoid bone, just above the cribriform plate. From there the upper border follows the midline of the vault on the inner surface of the frontal bone, along the sagittal suture between the parietal bones and down the occipital bone to the internal occipital protuberance. At the back the falx widens and blends with the top of the tentorium cerebelli, holding that sheet up like the ridge of a tent.

The falx carries dural venous sinuses in its edges. The superior sagittal sinus runs in its attached upper margin and drains much of the cerebral cortex; arachnoid granulations project into it to return cerebrospinal fluid to the blood. The inferior sagittal sinus runs in the free lower margin, curving above the corpus callosum. Where the falx meets the tentorium, the inferior sagittal sinus joins the great cerebral vein to form the straight sinus, which runs back in the line of that junction to the confluence of sinuses.

Mechanically, the falx limits side-to-side movement of the brain within the skull. When one hemisphere swells or is pushed by a mass, the cingulate gyrus can be forced under the free edge to the other side; this subfalcine herniation can kink the anterior cerebral artery. Patches of calcification in the falx are common with age and usually harmless, but they are a useful midline marker on X-ray and CT. Meningiomas may grow from it; falcine meningiomas lie hidden beneath the cortex and often press into one hemisphere.

Function and supply

Begins at

Attached in front to the crista galli of the ethmoid bone.

Ends at

Its upper border runs back along the midline of the vault to the internal occipital protuberance; behind, it fuses with the tentorium cerebelli along that sheet's crest.

Function

Separates and steadies the cerebral hemispheres, limiting their side-to-side movement, and carries the superior and inferior sagittal and straight sinuses.

Nerve supply

Sensory supply from meningeal branches of the ophthalmic nerve (tentorial nerve) and anteriorly from the anterior ethmoidal nerve; pain from it is felt as headache.

Blood supply

Meningeal branches, including the anterior meningeal branches of the anterior ethmoidal artery and branches of the middle meningeal artery.