ADULT CEREBELLAR MEDULLOBLASTOMA - IMAGING FEATURES WITH EMPHASIS ON MR FINDINGS

PURPOSE: To describe the MR imaging features of cerebellar medulloblas toma in the adult. MATERIALS AND METHODS: The neuroimages and records of 15 adults with proved cerebellar medulloblastoma were retrospective ly evaluated. In 12 patients, preoperative MR scans were reviewed; nin e had Gd-DTPA-enhanced scans. RESULTS: Of the 12 tumors evaluated preo peratively, eight were hemispheric, two hemispheric-vermian, and two v ermian. Tumor margins were well demarcated, except in three cases, two of which had large infiltrative tumors. In 10 cases, tumor extended t o the brain surface, and in five of these, contiguity with the tentori um or cerebellopontine angle cistern was such that an extraaxial tumor was considered. The tumors were typically hypointense on T1 but a spe ctrum was seen on T2-weighted images. Enhancement ranged from minimal and patchy to marked. One tumor became isointense after Gd-DTPA. Other features included cystic changes, hemorrhage, exophytic invasion at t he cerebellopontine angle, spinal cerebrospinal fluid seeding, intrave ntricular seeding, and bone metastasis. CONCLUSION: Although there is no pathognomonic MR appearance of adult cerebellar medulloblastoma, th e finding of a well-demarcated, mild to moderately enhancing hemispher ic mass involving the brain surface in a young adult is suggestive of medulloblastoma. Awareness that this tumor may resemble meningioma may avoid misdiagnosis and aid surgical planning.