MRI features of primary, secondary and metastatic medulloblastoma.

Medulloblastoma is the most frequent paediatric malignant brain tumour. The purpose of this study was to define imaging characteristics and contrast uptake patterns of primary and recurrent medulloblastoma using MRI. The MRI examinations of 17 histologically proven cases of medulloblastoma diagnosed in our institution (13 males and 4 females; mean age 13 years, 7 months) were reviewed in retrospect. Only patients with pre-treatment and follow-up examinations including T2-weighted images (fluid-attenuated inversion recovery or turbo spin echo) and T1-weighted images after contrast injection (0.1 mmol/kg Gd-DTPA) were included in this study. Whereas 6 of 7 tumours ( n=17) were hyperintense on T2-weighted images, contrast enhancement was detected in 13 patients. Fifteen tumours occurred in the cerebellar vermis, two were located in the cerebellar hemispheres. Mean size at the time of presentation was 30.1 mm. All patients presented with some extent of an occlusive hydrocephalus. Local recurrent tumour or metastases were seen in 6 patients (3 months to 7 years, mean age 2.5 years). Whereas the T2 signal intensity of recurrent tumour or subarachnoidal metastases resembled the primary neoplasms, the contrast uptake tended to be less pronounced ( n=3) or was completely absent ( n=2); thus, suggestive signs of primary medulloblastoma are location in the vermis, hyperintensity on T2-weighted images and hydrocephalus. The amount of contrast enhancement is variable and nonspecific. Secondary medulloblastoma manifestation is characterized by T2 hyperintensity but not by contrast uptake.