Adult cerebellar medulloblastoma: imaging features with emphasis on MR findings

To describe the MR imaging features of cerebellar medulloblastoma in the adult.

The neuroimages and records of 15 adults with proved cerebellar medulloblastoma were retrospectively evaluated. In 12 patients, preoperative MR scans were reviewed; nine had Gd-DTPA-enhanced scans.

Of the 12 tumors evaluated preoperatively, eight were hemispheric, two hemispheric-vermian, and two vermian. Tumor margins were well demarcated, except in three cases, two of which had large infiltrative tumors. In 10 cases, tumor extended to the brain surface, and in five of these, contiguity with the tentorium or cerebellopontine angle cistern was such than an extraaxial tumor was considered. The tumors were typically hypointense on T1 but a spectrum 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 the cerebellopontine angle, spinal cerebrospinal fluid seeding, intraventricular seeding, and bone metastasis.

Although there is no pathognomonic MR appearance of adult cerebellar medulloblastoma, the finding of a well-demarcated, mild to moderately enhancing hemispheric 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.