Adult‐onset medulloblastoma presenting with atypical MRI findings.

We report an extremely rare case of an 18‐year‐old girl with chronic progressive speech and gait disturbances due to abnormalities around the fourth ventricle, diagnosed as classic medulloblastoma with WNT signaling dysregulation by brain biopsy. Brain MRI showed atypical findings of symmetrical midline located adult medulloblastoma with no mass effect. PET‐CT scans revealed marked uptake of only 11C‐methionine. Medulloblastoma with atypical MRI findings should be considered in the differential diagnosis of tumors around the fourth ventricle in adults, even approximately symmetrical midline tumors with no mass effect. 11C‐methionine PET‐CT may be superior in detecting adult medulloblastomas with unique characteristics. [ABSTRACT FROM AUTHOR]