Wednesday 31 August 2011


An 18 yo male with nausea and vomiting.
Here is his Non contrast CT Brain, MRI Brain Axial T1, T2, FLAIR, Diffusion, Post contrast T1w images at the level of posterior fossa with single voxel MR Spectroscopy at TE of 35 ms.
This CT and MRI study of Brain shows:
A well circumscribed ovoid intra ventricular space occupying mass completely occupying and expanding fourth ventricle, leading to mild obstructive hydrocephalus. 
Lesion is solid, hyper dense on CT with spotty calcification at the center.
Signals isointense to cortical gray matter on T1 and FLAIR, slightly hyperintense on T2w images. No cystic component. No marked areas of necrosis. Restricted diffusion on MRI Dw images. Lesion is lobulated, mild heterogeneous enhancement on post contrast T1.
On MR Spectroscopy, no peak of NAA at 2.01ppm, no peak of creatine at 3.02 with long sharp peak of raised choline at 3.2ppm.
Here are MRI Axial T1, T2 and FLAIR images with post contrast T1w images of same patient at the level of lateral ventricles shows multiple discrete enhancing nodules along ependymal lining of lateral ventricles, signal of nodules on MRI are same as that of the posterior fossa mass with same restricted diffusion.

Imaging diagnosis : Medulloblastoma with Csf dissemination. 

Similar post:
Medulloblastoma MR Spectroscopy
Lateral origin medullobastoma


Syn: MB, Posterior fossa PNET, PNET – MB,
A highly cellular embryonal cell tumor.
Age group : common in children, ~75% diagnosed by 10 years.
3 times more common in males.

Intraventricular – 4th ventricular roof is a typical and most common location. A most common posterior fossa tumour in children.
Lateral origin – Cerebellar hemisphere is an atypical location common in older children and adults.

Size vary, average size ranges between 3- 5cm at the time of presentation.
On Non contrast CT, solid 4th ventricle mass, hyperdense, calcifcaiton seen in ~20% cases, small intra tumoural cysts, necrosis in ~50% cases.
On MR signal on T1 iso - hypo intense to cortical grey matter on T1 , iso – hyperintense on T2w and FLAIR. High signal on diffusion attributed to its dense, highly cellular nature.
An associated Obstructive hydrocephalus is common seen in ~ 95% cases.
Usually mild to moderate and homogenous enhancement, may show patchy heterogeneous enhancement due to areas of necrosis.
On MR Spectroscopy, NAA reduced or absent as it’s a non neuronal tumour, raised choline.

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