Midline oligodendrogliomas as studied by means of computed tomographic, angiographic, and positron-emission tomographic evaluations

Five patients with intraventricular oligodendroglioma involving the lateral ventricle were reviewed by computed tomography (CT), cerebral angiography, and positron-emission tomography (PET) to delineate specific neuroradiological features of the tumors in comparison to those involving the cerebral hemispheres. Intraventricular mass lesions, extending largely from the anterior horn to the body or trigone of the lateral ventricle, were seen as hyperdense tumors in 5 cases on CT; none was iso- or hypodense. Of particular note was the fact that all of the lesions demonstrated a homogeneous contrast enhancement. Calcification of varying sizes and shapes was found in 4 cases. Hypodense areas within the tumor matrix suggestive of cyst formation were found in 4 cases. In all 5 cases, asymmetrical dilatation of the lateral ventricle was noted. No peritumoral edema was demonstrated. On angiograms, in all cases the tumors were visualized as hypervascular, spaceoccupying mass lesions supplied by such feeding arteries as anterior and posterior choroidal, lenticulo-striate, thalamo-perforating, and pericallosal arteries. Among these arteries, either medial or lateral posterior choroidal arteries, or both, were commonly seen in these vascular tumors. Fine tumor vessels were also seen in the distal portion of these arteries. They were accompanied by a homogeneous tumor stain at either the late-arterial, capillary, or early-venous phase. PET was performed on a 21-year-old female. The PET images showed that the intraventricular tumor had an increased cerebral blood flow and volume at the tumor site, indicating a hypervascular tumor. However, this tumor was considered less malignant on the basis of its decreased rate of glycolysis, as evaluated by PET studies with 18-F-deoxyglucose. Lateral ventricular oligodendrogliomas, synonymously termed 'midline oligodendrogliomas,' have fairly specific neuroradiological features different from those of hemispheric oligodendrogliomas. (J.P.N.)