Adult-onset medulloblastoma presenting as slow-growing, atypical mass: a case report.

Medulloblastoma accounts for < 1% of all primary central nervous system tumours in adults. Although a "classical" imaging presentation -being a well-defined mass, often located in the cerebellar hemisphere, with surrounding oedema, showing iso- and heterogeneous signal intensity and contrast enhancement -has been described, case reports and series have also shown the extremely heterogeneous imaging aspect of this tumour , reflecting its heterogeneous molecular phenotype. Owing to the general location of the tumour within the cerebellopontine angle, causing (fast) progressive symptoms of headache and gait instability, most patients present within 3  months from symptom onset. This case report describes a presentation of adult medulloblastoma not shown before, with an indolent course over a period of 4.5  years, initially without clear abnormalities on imaging. It highlights the importance of including medulloblastoma in the differential diagnosis of all lesions found near/continuous with the fourth ventricle in the adult population, even when clinical onset and imaging characteristics do not suggest "classical" medulloblastoma.