The cerebellum is a thick, semicircular, tent-like septum that covers the cerebellum and separates it from the brain. The lamina that forms the cerebellum comes from a prolongation of the dura, the outermost of the meninges, which are the layers that cover the central nervous system (CNS).
It has a fixed edge (which is posterior) and a free edge (which is anterior). The fixed part is convex and inserts into the temporal bone, following a projection of the sphenoid bone until it reaches the occiput. For its part, the free edge acquires a concave shape and limits the orifice through which the brainstem opens.
Right lateral view of the skull. By Rabjot Rai, Joe Iwanaga, Gaffar Shokouhi, Rod J. Oskouian, R. Shane Tubbs - Rai R, Iwanaga J, Shokouhi G, Oskouian RJ, Tubbs RS. The Tentorium Cerebelli: A Comprehensive Review Including Its Anatomy, Embryology, and Surgical Techniques. Cureus. 2018; 10 (7): e3079. Published 2018 Jul 31. doi: https://dx.doi.org/10.7759%2Fcureus.3079, CC BY 3.0, This lamina is located in the posterior cranial fossa and divides the encephalic space into supratentorial, located above the cerebellum, and infratentorial, located below it.
The tent serves as a guide for the doctor when operating on a brain tumor, as different surgical techniques are used whether the lesion is above or below the tent.
Anatomy
The meninges are three membranes that cover the central nervous system and provide additional protection to that provided by the skeleton. From the inside out, the pia mater, arachnoid mater, and dura mater are recognized.
The first two are in close contact and communicated through a rich vascular network. As for the last, this constitutes the outermost and fibrous layer of the three. It is thick and resistant and forms three specialized partitions from extensions of its own structure.
From SVG by Mysid, original by SEER Development Team. Translated by Angelito7, Jmarchn - File: Meninges-en.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=29564005 These formations are located in the brain and are called: sickle cerebellum, falx cerebri and cerebellum tent.
The sickle of the brain separates the upper part of the two hemispheres of this organ; For its part, the falx cerebellum protects the neurological structure called the vermis that is located between the cerebellar lobes.
The tentorium cerebellum is the second largest reflection of the dura. It is located in the posterior cerebral fossa and separates the cerebellum from the temporal and occipital lobes of the brain.
It was first described in 1732 by the French anatomist Jacques Winslow, who included the term "cerebellum tent" in his publications regarding this structure.
This hard reflection divides the brain space into two parts, supratentorial and infratentorial. The infratentorial is occupied by the cerebellum and the brain troche. Thus, both parts are communicated in the free anterior border of the cerebellum, through the tentorial incisura, the area through which the brainstem passes.
Embryology
From the 16th day of gestation, the formation of the primitive central nervous system begins with the migration of cells that will give rise to the brain and spinal cord. Around these structures a cell covering forms that will give rise to the innermost layer of the meninges.
Towards 4 ta week primitive cerebellum complete their formation and can be seen a long cell layer in the cerebellar areas forming a middle portion of the store of the fetal cerebellum.
From Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See "Book" section below) Bartleby.com: Gray's Anatomy, Plate 649, Public Domain, https://commons.wikimedia.org/w/index. php? curid = 616454
The nuclei of some cranial nerves begin their training at the 5 ta week, and can be seen quite developed primitive dura. Covering these elements, a considerable number of cells are observed that will differentiate to form the skull.
Once formed the fetal cartilaginous skull, 7 ma week of gestation, the primitive dura is completely distinct and condensed.
The middle portion formed at the 4 ta week away and store the cerebellum can be seen in the location you will have after birth.
Inserts
The tentorium cerebellum runs in an upward direction from back to front and is located at the back of the fossa that houses the brain.
Its anterior border is concave, free of insertions and has a U-shape. It forms the posterior limit of the tentorial incisuration, which is the space through which the brainstem or brainstem passes.
By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See «Book» section below) Bartleby.com: Gray's Anatomy, Plate 766, Public Domain, https://commons.wikimedia.org/w/index. php? curid = 541612
In contrast, the posterior border is convex and fixed. This margin can in turn be divided into two parts, one internal and one posterior.
The internal portion is attached to the superior border of the petrous part of the temporal bone, while the posterior portion attaches to the anterior superior aspect of the occipital bone and the parietal bone.
Features
Since its first description in 1732, it is known that the term "tent" is not the most appropriate to describe this fibrous bundle of the dura mater.
Although it is located in the upper part of the cerebellum providing an additional protective layer, this septum fulfills a primary function as a support for the brain.
The cerebellum tent carries about 1,200 grams of brain weight and keeps the brain positioned in the brainstem.
Public Domain, It also prevents excessive movement of the brain in the case of trauma and deformities of the brain lobes.
In addition to this, it separates the brain space into the supra and infratentorial regions, depending on the location above or below the tent, which becomes important in brain surgery.
Clinical considerations
The technique used in the surgical approach to the brain depends on the location of the structure to be operated on.
To choose the best option, the cerebellum tent is used as an anatomical guide that, in addition to separating the encephalic space, is used as a route of entry to the cerebral elements.
Thus, those lesions located towards the external border of the cerebellum can be approached laterally, while for those located on the medial border, the occipital route is preferred.
In terms of pathologies, the increase in intracranial pressures caused by space-occupying injuries, such as tumors, hemorrhages or brain edema can cause a serious condition known as brain herniation.
Hernia is the protrusion of the brain from one cranial space to another. They are divided into supra or infratentorial.
Types of hernia: 1) Cingulum, below the falx cerebri. 2) Diencephalic, with descent of the brainstem 3) Transtentorial, over the cerebellum 4) Tonsillar, through the foramen magnum. From User: Delldot - self made, based on a diagram in: cite book author = Smith, Julian; Joe J. Tjandra; Gordon JA Clunie; Kaye, Andrew H.
In supratentorial cells, one of the most common sites for the exit of the brain is through the tentorial incisura, which is the space limited by the anterior border of the cerebellum, through which the brainstem passes.
For its part, in infratentorials the brain exerts great pressure on the tent, causing the cerebellum to protrude through the foramen magnum.
Brain herniation is a clinical and surgical emergency that must be treated immediately, as it can be fatal.
References
- Rai, R; Iwanaga, J; Shokouhi, G; Oskouian, R. J; Tubbs, RS (2018). The Tentorium Cerebelli: A Comprehensive Review Including Its Anatomy, Embryology, and Surgical Techniques. Taken from: ncbi.nlm.nih.gov
- Bordoni, B; Simonelli, M; Lagana, MM (2019). Tentorium Cerebelli: Muscles, Ligaments, and Dura Mater, Part 1. Cureus. Taken from: ncbi.nlm.nih.gov
- Bordoni, B; Simonelli, M; Lagana, MM (2019). Tentorium Cerebelli: the Bridge Between the Central and Peripheral Nervous System, Part 2. Cureus. Taken from: ncbi.nlm.nih.gov
- Bull, JW (1969). Tentorium cerebelli. Proceedings of the Royal Society of Medicine. Taken from: ncbi.nlm.nih.gov
- Lee, S. H; Shin, K. J; Koh, K. S; Song, WC (2017). Visualization of the tentorial innervation of human dura mater. Journal of anatomy. Taken from: ncbi.nlm.nih.gov