Tentorium cerebelli

The tentorium cerebelli is a horizontal crescent-shaped fold of dura mater forming the roof of the posterior cranial fossa. It separates the occipital lobes of the brain from the cerebellum and brainstem below.

The brain’s coverings, including the dura and arachnoid mater, obscure its intricate folds and grooves (sulci and gyri). However, in some regions, the inner layer of the dura mater extends into the brain, creating folds that connect to specific parts of the skull. These folds not only partition different brain areas but also provide structural support.

One such dural fold is the tentorium cerebelli, which derives its name from its tent-like shape. It covers structures within the posterior cranial fossa, specifically the cerebellum and brainstem. The tentorium cerebelli’s lateral edges attach to the occipital bone and house the right and left transverse venous sinuses. At its anterior edge, it attaches to the upper margin of the petrous temporal bone, where the superior petrosal venous sinuses are located.

The tentorium cerebelli also serves as a horizontal base for the attachment of two other dural folds: the falx cerebri above it, and the falx cerebelli below it. A small gap at the front of the tentorium cerebelli, known as the tentorial notch, allows the midbrain to pass through as it descends into the posterior cranial fossa, transitioning into the pons and medulla oblongata. Any bulging through this notch, such as the temporal lobes pushing through (uncal herniation), can compress the midbrain, impacting the oculomotor nerve and certain nerve fibers involved in movement, including the corticospinal and corticonuclear tracts.

In addition to the tentorium cerebelli, other important dural folds include the falx cerebri, falx cerebelli, and diaphragma sellae.