Lateral ventricular neoplasms of the brain: differential diagnosis based on clinical, CT, and MR findings.

The differential diagnosis of lateral ventricular tumors was explored by retrospective analysis of 47 pathologically proved cases identified by CT and/or MR imaging. Third ventricular tumors adjacent to the foramen of Monro (e.g., colloid cysts) were excluded. Forty-six patients underwent CT, and eight had MR imaging. The most common neoplasms were choroid plexus papilloma (10 cases) and meningioma (nine cases). Other common neoplasms included subependymoma (six cases), subependymal giant cell astrocytoma (five cases), and metastasis/lymphoma (four cases). Important features for differential diagnosis included age of the patient, the tumor's location within the lateral ventricle, and density on CT before IV administration of contrast material. Fifty percent of the tumors were in the ventricular atrium. All intraventricular tumor types (except subependymoma) showed contrast enhancement. MR was most useful in evaluating tumor location, size, and extent, but it did not help in eliminating alternative diagnoses. On the basis of patients' ages, specific tumor location, and the appearance on CT scans or MR images, an algorithm for differential diagnosis of lateral ventricular tumors was developed.