The tentorium cerebelli is a skin in the brain and separates the posterior fossa (fossa cranii posterior) from the middle fossa (fossa cranii media). The brainstem protrudes through the tentorial slit (incisura tentorii). Tears in the tissue can cause hemorrhage, possibly leading to midbrain syndrome.
What is the tentorium cerebelli?
The tentorium cerebelli represents an anatomical structure in the brain and is also known as the cerebellar vermis. It is located in the gap between the cerebrum and cerebellum (fissura transversa cerebralis). The tentorium cerebelli forms a duplication of the hard meninges (dura mater), which medicine also calls a duplication. The dura mater is one of three skins surrounding the central nervous system. Accordingly, a distinction is made between the spinal dura mater and the encephalic dura mater. The former encases the spinal cord, while the latter encases the brain. The tentorium cerebelli is not the only duplication of the dura mater. Other duplications of the hard meninges include the cerebral crescent (falx cerebri) between the two halves of the telencephalon and its continuation, the cerebellar crescent (falx cerebelli). The cerebellar crescent runs under the tentorium cerebelli, whereas the cerebral crescent joins the tip of the tentorium and pulls it forward.
Anatomy and structure
The tentorium cerebelli is attached to the sulcus sinus transversi, which forms a pit in the occipital bone (os occipitale). A blood duct passes through the pit, which anatomists refer to as the transverse sinus. In addition, the tentorium cerebelli attaches to the upper edge of the petrous bone (pars petrosa ossis temporalis). This bone part has the shape of a pyramid and is located at the temporal bone (Os temporale). As a duplication of the dura mater, the tentorium cerebelli consists of the inner leaf (lamina interna) of the dura mater. The skin consists of connective tissue. In the tentorium cerebelli there is a slit, the incisura tentorii. Through this opening, part of the brain stem exits the tentorium, which forms the tentorium cerebelli. In addition, the third cranial nerve (oculomotor nerve) and the fourth cranial nerve (trochlear nerve) pass through the incisura tentorii. In doing so, they accompany the posterior cerebral artery, which contributes significantly to the blood supply of the brain and embodies a branch of the basilar artery.
Function and Tasks
The main function of the tentorium is to separate the cerebellum from the cerebrum and to prevent excessive stress from pressure. It holds part of the cerebrum and supports it so that the cerebrum does not rest directly on the cerebellum. Since the cerebrum is responsible for about 80% of the brain mass, its weight would cause significant pressure between the two parts of the brain. The falx cerebri pulls the tentorium forward with the cerebrum and acts as a strap within the stabilization system. The support normally prevents the brain from skidding freely through the skull. The cerebrum or telencephalon is the seat of thought proper. Its functions include higher cognitive processes as well as preconscious and conscious sensory perception, motor function, emotions, learning, memory, and numerous other processes. The cerebellum or cerebellum also participates in learning and motor function, among other things. The tentorium cerebelli also protects blood vessels from high pressure. They could otherwise become congested or rupture. Furthermore, the tentorium cerebelli demarcates the posterior cranial fossa (fossa cranii posterior) from the middle cranial fossa (fossa cranii media). Both belong to the base of the cranium. The posterior cranial fossa contains the cerebellum and brainstem. Parts of the brain stem also protrude through the tentorium slit and provide a connection between the brain and the spinal cord as it proceeds. In contrast, the temporal lobe of the telencephalon is located in the cranial fossa media. The temporal lobe includes, for example, structures that contribute to the limbic system. Its functions include emotional processes, memory, learning, and autonomic control processes.
Diseases
A tear in the tentorium cerebelli can lead to hemorrhage, which then puts pressure on the brain, impairing its functions. Tentorium rupture is a possible complication of childbirth and represents a so-called birth trauma. In this context, medicine distinguishes between supratentorial and infratentorial hemorrhage.In supratentorial hemorrhage, the fluid backs up above the tentorium, that is, toward the cerebrum. In contrast, infratentorial cerebral hemorrhage takes place below the tentorium – toward the cerebellum. The escaping blood exerts pressure on the brain tissue, causing it to swell and become trapped in the tentorial slit. The temporal lobe and the uncus gyri parahippocampalis are particularly frequently affected by this. As a result, the development of midbrain syndrome is also possible. Its symptoms include increased muscle tone, restlessness, weakened corneal reflex, deviations of the eyeballs and pathological abnormalities of the pupil. In addition, the so-called doll’s head phenomenon is often observed: When the head is turned to the side, the eyes move with the head instead of continuing to look straight ahead by a countermovement of the eyeballs. In the most severe stage, midbrain syndrome leads to coma. Tentorium hemorrhage can be fatal. In particular, severe hemorrhages that spread widely are critical. Imaging techniques such as MRI and CT scan visualize the hemorrhage and allow doctors to pinpoint it as well as assess its extent. Surgery may be able to relieve pressure on the brain.
