الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Medulloblastma (MB) is a highly malignant (WHO grade IV), primitive cerebellar tumor of neuroectodermal origin. Medulloblastomas have been classified, based on histopathological, biological, and clinical characteristics, into classic medulloblastoma (CMB), desmoplastic nodular medulloblastoma (DNMB), medulloblastoma with extensive nodularity and anaplastic/large cell medulloblastoma.
Medulloblastoma shows heterogenous tumor features in each subtype. Based on these heterogeneity, magnetic resonance imaging (MRI) could differentiate pathological subtypes according to each imaging features.
This study aimed to assess the relation between Magnetic Resonance imaging features of pediatric medulloblastoma and pathological subtypes to improve treatment outcomes of the disease.
All patients were subjected to the following:
o History taking.
o Thorough clinical examination.
o Conventional MRI study of the brain.
o Susceptibility-weighted imaging of the brain with post processing phase image.
The study was applied on a 1.5 Tesla Magnetom Avanto Siemens (left handed system) machine using conventional MRI sequences in addition to DWI. Imaging evaluation depended on tumor location, tumor enhancement and degree of tumor restriction on DWI.
The 20 cases were selected ranged between 2-17 years old. They all underwent MRI study. The predicted imaging subtyping were correlated with the gold standard histo-pathological examination which showed total of 20 lesions: 14/20 lesions were central (Vermian) in location, 6/20 lesions were peripheral. 19/20 lesions showed hypo-intense signal on T1WI and 1/20 lesion showed iso-intense signal on T1WI. 13/20 lesions showed hyper-intense signal on T2WI and 7/20 lesions showed iso-intense signal on T2WI.
On post-contrast T1WI, 3/20 lesions showed minimal post-contrast enhancement, while 8/20 patients showed moderate heterogenous post-contrast enhancement and 9/20 patients showed intense homogenous post-contrast enhancement. All the lesions showed features of restricted diffusion. ADC value in all cases was found ranging from 0.56 to 0.94x10-6 cm/sec2
Magnetic resonance imaging was successful in differentiating 17/20 lesions according to different imaging features of each medulloblastoma pathological subtype which were matching with confirmed hiso-pathological study. In another meaning, 17 lesions were true positive & only 3 lesions were false negative giving MRI sensitivity 85%.
Histo-pathology remains the gold standard in differentiating subtypes, however we can use MRI in early prediction of the subtypes and early planning for their management, regardless MRI very important role in post-surgical assessment and follow up.