INTRACRANIAL SUBEPENDYMOMAS - CT AND MR-IMAGING FEATURES IN 24 CASES

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 stu dy was to characterize the differences in CT and MR imaging appearance s between subependymomas of the fourth and lateral ventricles, both of which were found in symptomatic patients. MATERIALS AND METHODS. We r etrospectively reviewed 24 pathologically proved cases of intracranial subependymomas in 17 male and seven female patients with a mean age o f 48.1 years. All patients were symptomatic. CT and MR images were use d to characterize the size, shape, and location of the subependymomas; the degree of hydrocephalus; tumor calcification; and the density, si gnal, and enhancement characteristics of the tumors. RESULTS. Eighteen of 24 tumors were 3 cm or more in greatest dimension. Nineteen were l obulated, and hydrocephalus was seen in 21. Fourteen were in the later al 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 enha ncement were in the fourth ventricle, and nine of 12 tumors with minim al or no enhancement were in the lateral ventricle. Small internal foc i with a signal intensity similar to that of CSF were seen on images o f all 10 lateral ventricular subependymomas obtained with both T1-weig hted and TS-weighted sequences. On 13 contrast-enhanced T1-weighted im ages, 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 s een in symptomatic middle aged adults and showed different CT and MR i maging features, depending on their anatomic location. Calcification a nd heterogeneous contrast enhancement were com mon features of fourth ventricular subependymomas seen on CT and MR images. Conversely, later al ventricular subependymomas showed a lack of calcification as well a s minimal or no contrast enhancement on CT and MR images.