[Common tumors of the fourth ventricle and cerebellum in childhood: evaluation of CT differential diagnosis].

Forty pediatric patients with infratentorial cerebellar astrocytomas, medulloblastomas and ependymomas were evaluated. In most cases it was possible to predict the histological type of these tumors by CT. The search for the residual fourth ventricle cavity and defining its location were the first step in differential diagnosis. The density of tumor on plain scans was of value to distinguish medulloblastomas from astrocytomas. Cerebellar astrocytomas had an obvious tendency to develop cystic change. Especially, the configuration of "Cyst-with-mural nodule" was the most specific characteristic in diagnosis. Just like medulloblastomas and ependymomas, cerebellar astrocytomas may have also the tendency to arise at the midline in childhood. The incidence of calcification was rather high in ependymomas.