Fourth ventricular mass MRI

A 7 y o female.

MRI BRAIN WITH MR SPECTROSCOPY
Sequences planned are FSE T1W, FSE T2W, FLAIR, T2w *GRE and DW images.
Post contrast T1w.
Axial T2w localizer taken and Single voxel MR Spectroscopy performed. The voxel of size 2x2cm placed over the lesion. Water suppression obtained was 99% with optimum spectral waveform obtained at short as well as long TE.
Non contrast CT.

Description of findings:

An ~50x40mm solid hyper dense well defined mass in the region of fourth ventricle on non contrast CT. Lesion is iso intense on T2 and FLAIR. High signal on Dw images. Avid enhancement on post contrast T1 marked at periphery.
Significant mass effect _ moderate obstructive hydrocephalus with mild peri ventricular ooze of Csf. Brain stem compressed.

MRI SPECTROSCOPY performed over lesion.
On short TE of 35ms and TR of 1500ms.
From right to left.
At 2.01ppm - short peak of NAA. NAA is reduced.
At 3.03ppm - short peak of Creatinine.
At 3.2ppm - sharp and long peak of Choline. High choline.
A peak of lactate at 1.4.
NAA/ Creatinine ratio is 1:1
Choline/ Creatinine ratio is 2:1

Imaging possible diagnosis: Medulloblastoma. 

Operated, posterior fossa craniotomy done.

Histopathology report 

Gross specimen : specimen consist of multiple irregular soft to friable pieces of dull – gray tan tissue. Representative sections submitted for processing. Codes : A and B.

Microscopy : sections A and B show a cellular neoplasm composed of medium sized cells with indistinct outlines and round oval or angular hyperchromatic nuclei varying in size. The larger nuclei show clumped chromatin. A fine fibrillary background is discerned between the cells at many places. Peri vascular arrangement of tumor cells with fibrillary processes arising from the cells and extending towards the blood vessels in the center are seen. The tumor is vascular and shows areas of hemorrhage.

Histopathological Diagnosis: Medulloblastoma. 

Similar cases of Medulloblastoma. 
Case 1 : Medulloblastoma MR Spectroscopy 
Case 2 : Medullobastoma lateral origin

MEDULLOBLASTOMA

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.

Location:
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.

Hemangioblastoma

Imaging findings:

A cystic mass with mural nodule at the floor of posterior cranial fossa.

Cyst is insinuating and descending down at foramen magnum, has clear fluid iso intense to Csf with thin imperceptible wall non enhancing on post contrast.

The eccentric round solid mural nodule, iso dense on CT, with intense homogenous enhancement on MR Post contrast T1. Flow voids in the mural nodule and adjacent to it. Imaging finding are very typical of a Hemangioblastoma. 

Significant mass effect on medulla and Pons with obstructive hydrocephalus.

A Glomus jugulare, a benign tumour with typical salt and pepper appearance noted as an incidental finding near left side jugular foramen.

Hemangioblastoma
A highly vascular tumor.
An intra axial posterior fossa mass with cyst and an enhancing mural nodule is a diagnostic clue.
Currently classified as meningeal tumor of uncertain histogenesis (WHO, 2000)
Locaion:
90% posterior fossa (m/c) in that 80% cerebellar hemispheres, 15% Vermis, 5% in other places  fourth ventricle, medulla.
10% Supratentorium.
In ~ 60% of cases mass present as cyst + mural nodule and in ~ 40% of cases only as a solid nodule.
Imaging:
Cyst is clear, density on CT and signal intensity on MRI same as that of Csf, non enhancing thin imperceptible wall.
Mural nodule on CT may be iso to hyper dense, intense and homogenous enhancement. On MRI hypo to iso intense on T1, hyperintense on T2 and FLAIR. May see flow voids within the nodule with adjacent vascular feeders on T2w images, intense and homogenous enhancement on T1 images implies to its highly vascular nature. May show low signal intensity hemosiderin staining on GRE if associated to with any bleed.

Presentation is usually with headache, dysequilibrium, dizziness may be due to its mass effect and hydrocephalus.
Age : for sporadic: 40-60 yr and for familial : can occur at younger age. Slight male predominance.


Closest DD is Pilocytic Astrocytoma; mural nodule show mild to moderate enhancement not this intense and homogeneous, not characterized by flow voids and feeders. Seen in relatively younger age group.