Introduction
Medulloblastoma is a malignant, embryonic brain tumor of the cerebellum, which is classified as the most severe grade according to the WHO classification of tumors of the central nervous system, i.e. grade IV. Despite its degree, it has a fairly good prognosis. With 30%, medulloblastoma is the most common brain tumor in childhood and adolescence.
Epidemiology
The frequency of brain tumors in general is said to be around 50 per 100,000 inhabitants and year. Among the primary brain tumors, medulloblastoma is a rather rare type of tumor with 5%. Nevertheless, at 30% it is the most common brain tumor in childhood and adolescence, with an annual incidence of 0.5 per 100,000 children under 15 years of age. The mean age of onset is 7 years, with boys being affected 2 to 3 times as often as girls. About a quarter of medulloblastomas occur in young adulthood, 70% of those affected are younger than 16 and very few are over 50 years old.
Localization
The medulloblastoma is mainly located in the cerebellar worm, the center of the cerebellum. Growing downwards, it fills the IV. ventricle, a cavity in the brain filled with cerebrospinal fluid (cerebrospinal fluid), and presses on the rearmost part of the brain, the medulla oblongata.
It pushes the cerebellar worm upwards and presses its front part against a part of the hard meninges (tentorium). Cells easily detach from the medulloblastoma and spread through the cerebrospinal fluid. The carry-over of tumor cells leads to the development of new tumors in other parts of the body.
The medulloblastoma can spread along the central nervous system via the cerebrospinal fluid (liquor). In this way, so-called daughter tumors (metastases) can develop on the meninges or in the spinal canal and cause further complaints. In one third of patients, such secondary tumors (metastases) are already detected at the time of initial diagnosis. Metastases in the cerebrospinal fluid occur in 15-40% of cases. Metastases outside the nervous system (extraneural) are rather rare in medulloblastoma, but occur in 4% of cases, mainly in bones and lymph nodes, but also in the liver and lungs.
