Rare Neoplastic Meningitis in Cerebellar Medulloblastoma Detected by PET/CT.

Neoplastic meningitis, also known as leptomeningeal metastases, is a rare clinical entity seen in less than 1%-2% of primary nervous system tumors. Diagnosis of leptomeningeal metastases is difficult and is achieved by cytologic evidence of malignant cells in cerebrospinal fluid, or demonstration of radiologic abnormality. 18 F-FDG PET/CT can detect leptomeningeal metastases before anatomical changes. In this case, a 42-year-old man with cerebellar medulloblastoma underwent surgery and radiotherapy and had FDG uptake in 3 separate locations after 3 months. The findings indicated leptomeningeal metastases, confirmed by MRI. This highlights the role of 18 F-FDG PET/CT in detecting leptomeningeal disease postmedulloblastoma treatment.