Intracranial oligodendrogliomas: imaging findings in 35 untreated cases.

The radiographic findings in 35 cases of untreated intracranial oligodendrogliomas were reviewed. The mean age of the patients was 34.6 years, and seizure disorder and headache were the most frequent presenting symptoms. Slightly less than two-thirds of the tumors were histologically pure and almost half were low-grade. Most lesions were cerebral and peripheral in location, and the majority were in the frontal lobes. On CT the tumors were usually hypo- or isodense. Contrast enhancement of tumor occurred in nearly half the cases, and was usually mild and poorly defined. Tumor calcification often occurred, and hemorrhage or cystic formation was not infrequent. Occasionally, calvarial erosion was associated with the tumors because of their peripheral location and slow-growing nature. The lesions were usually sharply demarcated and without edema. MR most frequently revealed hypointense lesions on T1-weighted images and abnormal hyperintensity on T2-weighted scans. In regard to grading or purity of oligodendrogliomas, no significant correlations were found except for a suggestion that higher-grade and mixed tumors tend to enhance more often on CT. The radiographic features of oligodendroglioma are quite characteristic but not pathognomic. A high preoperative suspicion might lead to more appropriate tumor management. MR, although less sensitive in detecting tumor calcification, is superior to CT in defining the tumor extent, which is beneficial for surgical and postsurgical radiotherapy planning.