Medulloblastoma dell'adulto:revisione di 9 casi studiati con la RM

Medulloblastoma is a neuroectodermic, malignant tumor of the cerebellum, most commonly seen in children and accounting for 25% of all intracranial neoplasms and 33% of posterior cranial fossa neoplasms in childhood. In adulthood, medulloblastomas account for 14-30% of medulloblastomas overall and 0.4%-1% of adult brain tumors. This study reviews 9 adult patients in order to characterize the neoplasm with regard to MR features. Five patients had lateral medulloblastoma, 3 paramedian and 1 median. On long TR/long TE images medulloblastomas generally had an intermediate to hyperintense signal; on short TR/short TE images tumor had a low to intermediate signal. Enhanced MR images were heterogeneous in 8 cases, while 1 case showed no enhancement. The vermian medulloblastoma presented no diagnostic problem. Paramedian medulloblastoma often appeared infiltrative. 3 lateral medulloblastomas appeared extra-axial and nimicked other masses of the cerebellopontine angle. In our series, one feature of potential differential importance was the angiographic hypovascularity of the medulloblastomas related to the tentorium. Hydrocephalus was present in 44% of patients. Cystic and/or necrotic changes within the tumor were seen in 33%. We conclude that the MR characteristics of medulloblastomas in adulthood are variable.