OBJECTIVETo explore the value of diffusion-weighted imaging (DWI),H-magnetic resonance spectroscopy (1H-MRS) and 3D whole-brain arterial spin labeling (3D ASL) in the diagnosis of medulloblastoma in the posterior cranial fossa.

METHODSThe magnetic resonance imaging (MRI) findings of 16 patients with pathologically confirmed medulloblastoma in the posterior cranial fossa were analyzed retrospectively. All the patients were examined with plane and enhanced brain MRI scans; 5 patients also underwent examinations with DWI, 12 with MRS, and 5 with 3D ASL.

RESULTSMedulloblastomas were found in the vermis and the fourth ventricle in 9 cases, in the cerebellar hemisphere in 5 cases, and in the cerebellopontine angle in 1 case; in 1 case multiple lesions were detected. The tumors showed iso-intense or slightly hypo-intense signals on TWI, and iso-intense or hyper-intense signals on TWI and FLAIR. The lesions showed high signals in DWI and low signals in ADC. Intra-lesion cysts were common (n=12), and calcification and bleeding were rarely seen. Mild patchy enhancement (n=6) or significant enhancement (n=10) was seen after contrast agent administration. Obstructive hydrocephalus was found in 12 cases and the subarachnoid space was involved in 3 cases. In all the 12 patients receiving MRS examination, high Cho and low NAA were found with significantly increased Cho/Cr (≥3.5) and Cho/NAA (≥4.0) ratios; Tau peak was seen in 8 cases, and Lip peak was found in 4 cases. All the 5 patients receiving 3D ASL examination showed decreased cerebral blood flow (CBF).

CONCLUSIONThe characteristic features of medulloblastomas in DWI, MRS and 3D ASL offer assistance to the diagnosis of atypical medulloblastoma.