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Teresa P. Morais, Mariana C. Diogo; Carla Conceição

Neuroradiology Department, Hospital Dona Estefânia, Centro Hospitalar de Lisboa Central (CHLC)

- Congresso Nacional SPNR, 1 a 4 de junho 2017, Estarreja

Background and Purpose: Medulloblastomas (MB) are the most common posterior fossa tumors of childhood. In recent years, a lot of attention has been drawn to their genetic diversity and its correlation with imaging characteristics, culminating with its integration in the 2016 WHO Classification of CNS tumors. Despite the utility of this correlation, MB should not be forgotten when atypical imaging presentations are seen. In this paper we present an atypical imaging presentation of MB, and discuss the findings and differential diagnosis.
Case presentation: A 5-year-old boy presented to the emergency department with headache and signs of intracranial hypertension. Computed tomography (CT) depicted an effacement of posterior fossa CSF spaces and acute hydrocephalus. MRI performed the next day showed multiple small T2-hyperintense masses conglomerated around the IVth ventricle walls, and smaller lesions in the cerebellar hemispheres, lateral ventricle walls, frontal cortex and around the spinal cord. They had no enhancement, no restricted diffusion and no defined primary mass. A biopsy was performed and histology results were compatible with a classic MB.
Discussion: With this case, we hope to bring attention to the fact that not all MB fit in the four WHO defined categories on imaging. Despite the absence of a defined mass, contrast enhancement or restricted diffusion, histology was still compatible with classic MB. In these cases, differential diagnosis includes rare entities, like diffuse leptomeningeal neuroglial tumor or infiltrative/infectious meningeal processes. We hope this case shows an interesting discussion of atypical presentations of MB and potential differential diagnosis.

Palavras Chave: Atypical imaging; DWI; Medulloblastoma; MRI; Multifocal