CT and MRI Findings of Malignant Meningiomas: Comparison with Benign Meningiomas

PURPOSE: The purpose is to evaluate the CT or MRI findings to help in the differentiation between benign and malignant meningiomas. MATERIAL AND METHODS: The CT and MRI findings of 8 patients with surgically proven malignant meningioma were reviewed. Four cases of 8 malignant meningiomas and 18 cases of 27 benign lesions were studied with a 1.5T or 0.5T MRI. Radiologic analysis was focused on the heterogeneity of tumor, grade of peritumoral edema, presence of cystic degeneration and calcification, tumoral enhancement pattern, dural enhancement, and tumoral border. RESULT: Histologic types of malignant meningioma were meningotheliomatous (n=4), papillary(n=1), fibroblastic(n=l), angioblastic(n=l), and sarcomatous(n=l). Tumoral Heterogeneity was seen in 8 of 8 malignant lesions(100%) and 8 of 27 benign ones(30%). (p<0.01) Marked peritumoral edema was seen in 8 of 8 malignant lesions(100%) and 2 of 27 benign ones. (7.3%)(p<0.01) Most of malignant lesions(6 of 8 cases, 75%) showed ill defined border. Calcification was not present in malignant lesions in contrast with benign ones (14 of 27 cases, 52%). (p<0.05) No statistical significance was noted in cystic degeneration, dural tail like enhancement or tumoral enhancement pattern between malignant and benign meningiomas. MRI signal intensity of malignant meningiomas was homogeneously or heterogeneously hypointense on T1WI, heterogeneously isointense or hypointense on T2WI and heterogeneous or mixed on Gd-DTPA enhancement study. CONCLUSION: The CT or MRI findings such as heterogeneity, ill defined tumoral border, marked peritumoral edema, and absence of calcification may suggest the possibility of malignancy in meningioma.

Radiologic Features of Posterior Fossa Hemangioblastomas: Emphasis on MR Findings

PURPOSE: To review MR findings of the posterior fossa hemangioblastomas and to evaluate diagnostic value of MRI correlated with CT and anglographic findings. MATERIALS AND METHODS: The MR findings in twelve patients with surgically proven posterior fossa hemangioblastomas including one case of von Hippel- Lindau disease were retrospectively analyzed and correlated with CT (7 patients) and anglographic findings (9 patients). RESULTS: On MRI, five hemangioblastomas were located in the cerebellar hemisphere and seven in the vermis. The masses appeared to be solid in 3 cases(25%), solid tumors with central cyst in 2 cases(17%), and cyst with mural nodules in 7 cases(58%). Abnormal tumor vessels represented by characteristic signal voids on MRI were observed in 9 cases(75%) and were not seen in 3 cases(25%) with mural nodule below 1.5cm in diameter. On pre-contrast CT, hemangioblastomas appeared poorly marginated slightly hyperdense masses in solid tumors, and hypodense cystic masses in cysts. After contrast enhancement, solid tumors were markedly enhanced, but it was difficult to differentiate hemangioblastomas from other tumors. In nine patients, anglograms demonstrated hypervascular blush corresponding to the solid component of the tumors. CONCLUSION: MRI was superior to CT in evaluating the characteristic of abnormal tumor vessels and mural nodules, delineation of tumor margin and tumor extent. Angiography was useful in the diagnosis of cystic hemangioblastomas which contain small mural nodule (less than 1.5cm in diameter) without definite vascular signal voids on MRI. MRI demonstrated solid or cystic tumor with small mural nodule and abnormal vascular signal voids in the posterior fossa should suggest hemangioblastoma.