"Primary" leptomeningeal dissemination of medulloblastoma. Report of an unusual case.

The Authors report the case of a 5-year-old boy medulloblastoma presenting with "primary" widespread diffusion in the subarachnoid spaces of the posterior fossa without true mass lesion. The diagnosis, suspected first on the basis of the computed tomography (CT) findings, was confirmed by cytological examination of the cerebrospinal fluid (CSF) and by surgery. The Authors analyse the peculiar clinical features (rapid and severe deterioration of general conditions, hyperacute course of the illness and fatal issue) and the morphological aspects of the tumor (CT and surgical findings). To our knowledge no case of "primary" dissemination of medulloblastoma was previously reported.