Findings
A midline intraaxial SOL involving the cerebellar parenchyma.
Perilesional edema with mass effect on the fourth ventricle and cerebral aqueduct. Resultant significant dilatation of the supratentorial ventricular system, mild inferior tonsillar herniation.
Compression and anterior displacement of the brain stem.
The lesion is predominantly solid. Enlarged peritumoral and intratumoral vessels appearing as curvilinear flow voids in the vicinity of the lesion.
Perfusion study shows markedly elevated cerebral blood volume and flow in the lesion
Post contrast T1 weighted images show intense enhancement of the tumor.
MR spectroscopy of the lesion shows diminished NAA and elevated Cho/Cr ratio in the lesion ( 2.13 ) as compared to normal reference voxel (0.72 ).
Screening study of the spine shows no metastasis.
Posterior fossa intra-axial mass in an adult (middle/old age)
Most common cause is METASTASIS.
Second most common cause - HEMANGIOBLASTOMA.
HEMANGIOBLASTOMA
- Characteristically, an intra-axial posterior fossa mass in an adult, consisting of a cyst with an enhancing mural nodule abutting pia.
May be predominantly solid (as in this case).
- constitute 10% of posterior fossa tumors.
- may occur as a part of VHL syndrome. ( multiple hemangioblastomas, visceral cysts, RCC, positive family history)
CT - cyst with mural nodule, showing post contrast enhancement.
MR - T1WI - isointense +/- flow voids.
T2 - hyperintense.
FLAIR - hyperintense.
Post contrast - intense enhancement.
METASTASIS - Mets with high vascularity (as may occur in RCC)may have a very similar appearance, a close differntial. However, lesions usually multiple in such cases.
GLIOBLASTOMA usually occur in supratentorial compartment. An infratentorial glioblastoma may cause confusion. Here, central necrosis and enhancing rim are prominent features.