The tentorium cerebelli (Latin for "tent of the cerebellum") is an invagination of the meningeal layer of the dura mater that separates the occipital and temporal lobes of the cerebral hemispheres from the cerebellum and brainstem. This sheet extends in the axial plane over the posterior cranial fossa, divides the cranial cavity into the supratentorial and infratentorial spaces and covers the cerebellum like a tent (hence its name!).
In terms of function, the tent shape of the tentorium cerebelli ensures that the cerebellum and underlying brainstem are protected from the pressure caused by the heavier upper part of the brain.
This article will discuss the anatomy and function of the tentorium cerebelli.
|Definition||The tentorium cerebelli is an invagination of dura mater that separates the occipital and temporal lobes of the cerebrum from the cerebellum and brainstem.|
Anterior margin: Anterior clinoid process
Lateral margin: Superior border of the petrous part of the temporal bone, posterior clinoid process
Posterior margin: Internal occipital protuberance, lips of the groove for transverse sinus
Anterior margin: Cavernous sinus
Lateral margin: Superior petrosal sinuses
Posterior margin: Transverse sinus
Posterior part: Straight sinus
|Function||Protects the cerebellum and infratentorial brainstem from pressure by suspending the lobes of the brain.|
The brain and spinal cord are enveloped by the meninges, which serve to protect them from mechanical trauma, provide support to blood vessels and a passageway for the cerebrospinal fluid (CSF). From innermost to outermost, the meninges consist of the following three layers: pia mater, arachnoid mater, and dura mater.
The dura mater is a strong, double-layered membrane, composed of the periosteal layer, which adheres to the periosteum of the neurocranium, and the meningeal layer, which surrounds the brain and spinal cord. In some regions and fissures of the brain, the meningeal layer of dura mater projects inwards to form four dural partitions: the falx cerebri, falx cerebelli, tentorium cerebelli, and sellar diaphragm.
The tentorium cerebelli is the second-largest dural reflection that extends over the posterior cranial fossa. It separates the occipital and temporal lobes of the cerebrum from the underlying cerebellum and brainstem, and divides the cranial cavity into supratentorial and infratentorial spaces.
The tentorium cerebelli is attached almost along the entire circumference of the posterior cranial fossa with its outer (posterior and lateral) margins, which are fixed and convex. The inner (anterior) margin is free and concave, and forms a U-shaped hiatus.
- The posterior margin is attached to the internal occipital protuberance in its most posterior aspect, and continues along the lips of the groove for transverse sinus. As it extends further anteriorly, it attaches to the posteroinferior angles of the parietal bone.
- The lateral margin is attached to the superior border of the petrous part of the temporal bone, and extends anteriorly to attach on the posterior clinoid process. As it reaches the apex of the petrous temporal bone, it continues anteriorly as a dural ridge called the posterior petroclinoidal ligament.
- The free anterior margin contains a large U-shaped hiatus called the tentorial notch, which provides passage to the midbrain and the superior aspect of the cerebellar vermis. In addition, the splenium of the corpus callosum occupies a small part of the tentorial notch. The rim of the tentorial notch is attached to the apex of the petrous temporal bone and extends anteriorly as the anterior petroclinoidal ligament to attach to the anterior clinoid process.
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The tentorium cerebelli contributes to the formation of several dural venous sinuses and one dural recess:
- The posterior margin of the tentorium cerebelli houses the transverse sinus, running along the groove for transverse sinus on the occipital bone.
- The superior surface of the posterior part of the tentorium cerebelli blends with the falx cerebri. This line of attachment contains the straight sinus.
- The lateral margin of the tentorium cerebelli houses the superior petrosal sinus, which runs in the superior border of the petrous part of temporal bone.
- The site where the free anterior margin adheres to the anterior clinoid process forms the lateral part of the cavernous sinus.
- Near the apex of the petrous temporal bone, the lower layer of the tentorium is evaginated anterolaterally under the superior petrosal sinus to form a dural recess, the Meckel’s cave. Meckel's cave houses the posterior root of the trigeminal nerve and the trigeminal ganglion.
To learn more about the dural venous sinuses, check out our study unit below, and then take the custom quiz to see how well you retained the information!
As higher primates evolved from quadrupedal to bipedal locomotion with erect posture, the tentorium cerebelli came into play to support the extra weight of the brain that shifted from the anterior aspect, to the superior aspect of the cervical spine. Thereby, the tentorium cerebelli adds strength to the axial midline and dispels the burden of weight from supratentorial structures on the infratentorial structures.
In addition, it is thought that the dural folds, and especially the falx cerebri and the tentorium cerebelli, play an important role in the development and functional loading of the cranium. In other words, dural folds determine the cranial suture sites and their absence is accompanied by a lack of suture formation.
Now that you’ve completed this lesson, take the following quiz to test and consolidate your knowledge about the tentorium cerebelli and other meningeal structures of the brain!
Transtentorial herniations are cerebral herniations in which a part of the brain moves from one compartment to another across the tentorial notch of the tentorium cerebelli. It can be caused by anything that increases the intracranial pressure in one compartment of the brain, such as a tumor, localized hemorrhage (e.g. epidural hematoma), or an increase in cerebrospinal fluid (CSF) volume. There are three ways by which a transtentorial herniation can occur: uncal, central and upward herniation.
An uncal herniation refers to the downward displacement of the uncus of the temporal lobe. It is caused by a unilateral mass effect from within the cerebral hemispheres, that pushes the uncus downwards and medially across the tentorial notch. The herniated uncus can compress the brainstem, oculomotor nerve (CN III) and posterior cerebral arteries in the ambient cistern.
A central herniation refers to the downward displacement of the diencephalon and midbrain. In contrast to uncal herniation, central herniation is caused by a bilateral mass effect or diffuse brain edema, that pushes the diencephalon and midbrain centrally through the tentorial notch.
An upward herniation refers to the upward displacement of structures that are below the tentorial notch. These herniations are caused by a mass effect within the posterior cranial fossa that pushes the superior parts of the cerebellum upwards through the tentorial notch.
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