Objective: The intracranial subependymoma is a benign glioma that has been classically described as an asymptomatic fourth ventricular tumor found incidentally at autopsy in elderly men. The purpose of this study was to characterize the differences in CT and MR imaging appearances between subependymomas of the fourth and lateral ventricles, both of which were found in symptomatic patients.
Materials and methods: We retrospectively reviewed 24 pathologically proved cases of intracranial subependymomas in 17 male and seven female patients with a mean age of 48.1 years. All patients were symptomatic. CT and MR images were used to characterize the size, shape, and location of the subependymomas; the degree of hydrocephalus; tumor calcification; and the density, signal, and enhancement characteristics of the tumors.
Results: Eighteen of 24 tumors were 3 cm or more in greatest dimension. Nineteen were lobulated, and hydrocephalus was seen in 21. Fourteen were in the lateral ventricle, and 10 were in the posterior fossa. Calcifications were present in five (all fourth ventricular) and absent in 10 (all lateral ventricular) subependymomas imaged with unenhanced CT. On 18 contrast-enhanced CT scans, five of six subependymomas with heterogeneous enhancement were in the fourth ventricle, and nine of 12 tumors with minimal or no enhancement were in the lateral ventricle. Small internal foci with a signal intensity similar to that of CSF were seen on images of all 10 lateral ventricular subependymomas obtained with both T1-weighted and T2-weighted sequences. On 13 contrast-enhanced T1-weighted images, seven of eight tumors with heterogeneous enhancement were in the fourth ventricle, and all five with minimal or no enhancement were in the lateral ventricle.
Conclusion: Intracranial subependymomas were seen in symptomatic middle-aged adults and showed different CT and MR imaging features, depending on their anatomic location. Calcification and heterogeneous contrast enhancement were common features of fourth ventricular subependymomas showed a lack of calcification as well as minimal or no contrast enhancement of CT and MR images.