The posterior cranial fossa forms the posterior fossa of the skull. It contains the medulla oblongata (medulla oblongata), bridge (pons), midbrain (mesencephalon), and cerebellum (cerebellum).
What is the posterior cranial fossa?
The posterior cranial fossa is the posterior fossa of the skull. The posterior cranial fossa is adjacent to the middle cranial fossa (fossa cranii media), which contains the temporal lobe of the cerebrum (telencephalon). In contrast, the anterior cranial fossa (fossa cranii anterior) contains the frontal lobe of the cerebrum. These three cranial fossae belong to the base of the skull (basis cranii) and as such constitute part of the cranium (neurocranium). The boundary between the fossa cranii media and the fossa cranii posterior is formed by the cerebellar tentacle, also known as the tentorium cerebelli, which has a slit through which the brainstem protrudes. The medulla oblongata (medulla oblongata), bridge (pons), midbrain (mesencephalon), and cerebellum (cerebellum) are located in the cranii posterior fossa.
Anatomy and structure
The posterior cranial fossa contains passageways for nerves, arteries, and veins. The largest opening is the foramen magnum, which is located in the middle of the posterior fossa. The elongated medulla enters the cranial cavity through the oval-shaped passage. The medulla oblongata is joined inferiorly by the spinal cord, while in the brain it merges into the bridge. The eleventh cranial nerve (nervus accessorius), the wing ligaments (ligamenta alaria), as well as the arteriae spinales and the spinal vein also pass through the foramen magnum. In addition, the hard meninges (dura mater) merge into the membrana tectoria at the opening. Next to the foramen magnum is the hypoglossal canal (Canalis nervi hypoglossi), through which the twelfth cranial nerve of the same name passes. In contrast, the seventh cranial nerve (facial nerve), the eighth cranial nerve (vestibulocochlear nerve) as well as the labyrinthine artery and the labyrinthine vein run through the internal acustic porus. Below the porus acusticus internus is the foramen jugulare, where the internal jugular vein originates. In addition, cranial nerves IX-XI, the ascending pharyngeal artery, and the inferior petrosal sinus cross the jugular foramen. The condylar foramen houses an emissary vein. The posterior cranial fossa also has other, smaller openings.
Function and Tasks
The fossa cranii posterior forms part of the skull base, which embodies the floor of the cerebral skull. Within it are parts of the brain: the medulla oblongata, the pons, the midbrain, and the cerebellum. The medulla oblongata is an extension of the spinal cord, which is the transition to the brain. From there, the human body controls autonomic functions such as breathing and circulation, as well as numerous reflexes – including those to swallow, vomit and cough. The pons interconnects nerve fibers in its core areas, also known as the nuclei pontis. The formatio reticularis also extends through the pons as a network of nerve cells. However, many nerve tracts pass through the bridge without being switched. These pathways lead to the cerebrum and medulla oblongata as well as to the cerebellum. Medicine also groups the medulla oblongata and bridge together to form the rhombic brain (rhombencephalon). Together with the midbrain (mesencephalon), they represent the brainstem. The midbrain is also located in the fossa cranii posterior. It includes the capsula interna, which comprises numerous neural pathways of the brain. The midbrain participates in the control of movements, making use of the extrapyramidal motor system. The cerebellum also deals with motor tasks, taking into account, among other things, posture. In addition, it contributes to the movement control of the eyes. In addition, the cerebellum participates in implicit learning processes.
Diseases
Increased intracranial pressure can cause the tentorial slit, located in the cerebellar vermis, to pinch portions of the brain. As a result, midbrain syndrome, also known as mesencephalic syndrome, manifests. Medical science divides the condition into three stages depending on its severity. Symptoms of midbrain syndrome include quantitative disturbances of consciousness up to coma, striking pupillary reactions, increased muscle tone, and unusually high reflexes (hyperreflexia).Various causes can be considered for an increase in intracranial pressure: space occupying tumor, cerebral edema, hematoma, cerebral contusion (compressio cerebri), and others. Tentorial tear often results in hemorrhage and can put pressure on the brainstem. Frequently, the tear occurs as birth trauma. The capsula interna in the midbrain can be damaged in the course of a stroke, which is due to a disturbance of blood flow to the brain. Since motor nerve pathways also run through the capsula, a lesion of the internal capsule eventually leads to hemiparesis in that half of the body opposite the damage. As brainstem syndromes, medicine summarizes a number of clinical pictures that result from damage in this region. An example of a brainstem syndrome in the presence of damage to the medulla oblongata (oblongata syndrome) is Jackson syndrome. Typical symptoms include paralysis of the extremities on the side of the brain lesion and opposite paralysis of the hypoglossal nerve. Impaired blood flow in the vessels supplying the medulla oblongata is the most common cause of Jackson syndrome. In principle, severe damage to the brainstem can also be fatal, as it controls numerous functions necessary to sustain life. These include breathing, for example.
