Abstract：Objective: To discuss the MRI diagnostic value of the fourth ventricular tumors in children. Materials and Methods: Eighteen cases of pediatric fourth ventricular tumors proved by surgery and pathology were reported. The routine and post-contrast images were obtained by a 1.5T MR scanner. Results: There were 7 medulloblastomas, 7 astrocytomas, 3 ependymomas, and 1 schwannoma. Most tumors demonstrated as low signal intensity on T1WI and high signal intensity on T2WI. Medulloblastomas originated from cerebellar vermis. Six of them had small cysts and one of them had bleeding within the tumor. They all enhanced strongly. Five astrocytomas originated from cerebellar vermis and one from brain stem. Most of them had big cysts with semi-rim like circular enhancement or rim-like circular enhancement. Enhanced nodules can also be seen. The poor differentiated ones were irregular in shape with more nodules. Two ependymomas originated from fourth ventricle with small cysts inside. One ependymoma originated from cerebellar vermis with big cyst formation. One schwannoma originated from fourth ventricle. The upper part enhanced strongly and lower part was a big cyst without enhancement. Conclusion: MR examination is very useful in the assessment of pediatric fourth ventricular tumors.
2008, Vol. 19 
