Accepted
at 3:42 a.m. Jun, 23, 2024
by
stumphickory
Author:
Solar04
Type of change:
Updated content
Rationale for change
Changed cloze for genetic mutation to age group.
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*2021 WHO update (source: radiopaedia):
Features of medulloblastoma (radiopaedia, imaging from multiple different cases):
Gross Path -
The image shows soft, fleshy tumor with areas of softening and necrosis in the center. Although the tumor appears well-circumscribed, there is usually some infiltration at the edges into the surrounding brain parenchyma. Microscopic path would show a small round blue cell tumor.
CT
Hyperdense mass within the central posterior fossa causing obstructive hydrocephalus (note interstitial edema).
MRI
https://radiopaedia.org/articles/medulloblastoma
"In the 2016 edition of the WHO classification of CNS tumors, four molecular groups were recognized (WNT, SHH, group 3 and group 4). In the 5th edition (2021) of the WHO classification of CNS tumors, new subgroups were acknowledged based on DNA-methylation profiling and/or transcriptome profiling 17. Additionally, the four histopathological types described in the 2016 edition were combined into one section that describes them as morphologic patterns of one tumor group: medulloblastomas, histologically defined 23."
Features of medulloblastoma (radiopaedia, imaging from multiple different cases):
Gross Path -
The image shows soft, fleshy tumor with areas of softening and necrosis in the center. Although the tumor appears well-circumscribed, there is usually some infiltration at the edges into the surrounding brain parenchyma. Microscopic path would show a small round blue cell tumor.
CT
Hyperdense mass within the central posterior fossa causing obstructive hydrocephalus (note interstitial edema).
On CT, medulloblastomas often appear as a mass arising from the vermis, resulting in effacement of the fourth ventricle / basal cisterns and obstructive hydrocephalus. They can also occur more laterally in the cerebellum.
They are usually hyperdense (90%) and cysts formation/necrosis is common (40-50%), especially in older patients. Calcification is seen in 10-20% of cases 7.
Enhancement is present in over 90% of cases and is usually prominent 7.
MRI
- T1
- hypointense to grey matter
- T1 C+ (Gd)
- overall 90% enhance, often heterogeneously (tumors in adults tend to have less degree of enhancement compared to the pediatric population24)
- WNT-activated tumors tend to vividly enhance 17
- group 4 tumors tend to enhance less 10
- T2/FLAIR
- overall are iso to hyperintense to grey matter
- heterogeneous due to calcification, necrosis and cyst formation
- surrounding edema is common 10
- DWI/ADC
- high DWI signal ("restricted diffusion") - due to their hypercellularity
- low ADC values (lower than normal cerebellum e.g. ~550 x 10-6 mm2/s) 11
Personal Notes
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Missed Questions
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Core Radiology
Fundamentals of Diagnostic Radiology
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Crack the Core
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War Machine
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Sectional Anatomy
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Additional Resources
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One by one
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Section Title
Neuroimaging Brain: Posterior Fossa Intra-Axial Tumors