Pediatric Intra-Fourth-Ventricular Tumors: MR Imaging Findings with Emphasis on Features Indicating Likely Histological Diagnosis

Abstract

The fourth ventricle is one of the most common locations of various histological types of pediatric brain tumors. A histological diagnosis is an important aid in predicting prognosis and selecting the most appropriate treatment regimen. The purpose of this study was to determine the value of MR imaging in the diagnosis and differential diagnosis of pediatric intra-fourth-ventricular tumors (PITs). The clinicopathological data and MR findings of 23 pathologically verified cases of PITs were analyzed retrospectively with special emphasis on features indicating a histological diagnosis. There were ten females and 13 males in the study group aged from 11 months to 18 years, mean age 11 years. The main presentations were the symptoms and signs of raised intracranial pressure. Of 23 cases of PITs, there were eight medulloblastomas showing T1 hypointensity, marked enhancement, and T2 hyperintensity with a vague margin. Six astrocytomas, among which cyst formation was common, did not enhance with Gd-DTPA. No hemorrhage or calcification was demonstrated. The ependymomas (six cases) tended to expand within the fourth ventricle in a plastic-like fashion and showed hypointensity on T1WI and hyperintensity on T2WI with vague margins. Two choroids plexus papillomas appeared as isointense to hypointense masses with marked Gd-DTPA enhancement on T1WI and variable hyper- to hypointensity to CSF on T2WI. One case of epider-moid cyst was characterized by predominantly low intensity and high intensity signals on T1-weighted and T2-weighted imaging. It may be difficult to suggest a histological diagnosis on the basis of signal intensity features on MRI alone. In combination with the patient's age, anatomic localization, and morphology characteristics, MRI is of great value in the differential diagnosis of PITs.