Tentorium cerebelli

At a glance

English

Tentorium cerebelli

Latin (TA2)

Tentorium cerebelli

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the tentorium cerebelli

Named from the Latin for the cerebellum's tent, the tentorium cerebelli is a crescent-shaped sheet of dura mater that roofs the posterior cranial fossa. It lies between the upper surface of the cerebellum and the undersurface of the occipital lobes, which it supports. It is highest in the midline and slopes down towards its edges, like a tent, because the falx cerebri is attached along its upper surface in the midline and pulls it upward. The space above it is called supratentorial and the space below infratentorial.

The tentorium has two borders. Its outer, attached border is convex. Behind, it is fixed to the lips of the grooves for the transverse sinuses on the occipital bone, which it encloses; at the sides it is fixed to the upper border of the petrous temporal bone, where it encloses the superior petrosal sinuses. Its inner, free border is concave and surrounds a large gap, the tentorial notch, through which the midbrain passes. Near the apex of the petrous bone the two borders cross: the free border runs forward to the anterior clinoid process and the attached border to the posterior clinoid process. Here a small pocket of dura beneath it forms the trigeminal cave. Along the line where the falx cerebri meets the tentorium runs the straight sinus.

By dividing the cranial cavity, the tentorium limits movement of the brain within the skull and keeps the weight of the cerebral hemispheres off the cerebellum. The margin of the notch lies close to the midbrain, the oculomotor and trochlear nerves, the posterior cerebral arteries and the uncus of the temporal lobe.

When a mass or bleed above the tentorium raises pressure, the uncus can be pushed down through the notch. This transtentorial herniation squeezes the oculomotor nerve, giving a dilated pupil on the same side, and then compresses the midbrain, which is an emergency. Brain tumours are classed as supratentorial or infratentorial, and most childhood tumours lie below the tentorium. Small calcifications in the tentorium are common in older people and usually harmless.

Function and supply

Begins at

Attached behind to the margins of the transverse sinus grooves on the occipital bone and laterally to the upper border of the petrous temporal bone.

Ends at

Its free border runs forward to the anterior clinoid processes and its attached border to the posterior clinoid processes of the sphenoid bone; the falx cerebri joins its upper surface in the midline.

Function

Separates the occipital lobes from the cerebellum, supports the weight of the cerebral hemispheres and encloses the transverse, superior petrosal and straight sinuses.

Nerve supply

The tentorial (meningeal) branch of the ophthalmic nerve; pain from it is felt in the forehead and behind the eye.

Blood supply

Tentorial branches of the meningohypophyseal trunk of the internal carotid artery, with meningeal branches of the middle meningeal and occipital arteries.