First used by Bailey and Cushing in 1925  , the term medulloblastoma described a series of tumors found in the cerebella of children. Originally classified as a glioma, medulloblastoma is referred to now as a primitive neuroectodermal tumor (PNET). This tumor accounts for approximately 7-8% of all intracranial tumors and 30% of pediatric brain tumors.
In the brain, medulloblastoma most often arises in the posterior fossa as shown in the image below. The tumor has the propensity of spreading throughout the CNS. Systemic metastases of this tumor, especially to bone, also have been recognized.
Incidence of medulloblastoma is 1.5-2 cases per 100,000 population, with 350 new cases in the United States each year. Although the majority occur as sporadic cases, hereditary conditions have been associated with medulloblastoma, including (1) Gorlin syndrome (nevoid basal cell carcinoma syndrome), (2) blue rubber-bleb nevus syndrome, (3) Turcot syndrome (eg, glioma polyposis syndrome), and (4) Rubinstein-Taybi syndrome.
Incidence of medulloblastoma worldwide seems to approximate that in the United States.
See the list below:
Hydrocephalus: The most common complication is hydrocephalus due to compression of the normal cerebrospinal fluid (CSF) pathways. Although this is a common complication, only 10-50% of patients with preoperative hydrocephalus will need a long-term ventricular shunt. Some children can be treated with an endoscopic third ventriculostomy.
Cerebellar dysfunction: Tumor infiltration of the cerebellum usually is in the midline, leading to difficulties with ambulation and truncal ataxia. This is more common than signs attributable to the cerebellar hemisphere (eg, extremity dysmetria).
Leptomeningeal dissemination: One of the most feared complications of medulloblastoma is dissemination within the CSF. Medical and, less commonly, surgical therapy must be directed at controlling dissemination to cranial nerves and spinal cord and related structures. This dissemination of disease portends to a high-risk stratification.
No specific predilection for a particular racial or ethnic group has been noted.
Medulloblastoma is more common in males than females (1.5:1). Males also tend to have a poorer prognosis.
Although predominantly a pediatric tumor, medulloblastoma can affect patients of any age from neonates to the elderly. Three quarters of all cases occur in children, with a median age of 9 years.
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