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- bilateral fronto-parietal predominantly peri-ventricular and subependymeal multi-focal mass lesion is seen infiltrating the forceps major and the corpus callosum. The mass measures 4.9 X 4.3 X 2.5 cm in its main axial and CC dimensions. The mass shows hypointense T1 and iso- to mildly hypointense T2 signal with evident restricted diffusion. The lesion shows predominantly marginal post-contrast enhancement with solid enhancing lesion at the left high posterior frontal subependymal region.
- the mass is associated with mild perifocal vasogenic brain oedema with compression of the posterior portions of the lateral ventricles’ bodies.
- multi-voxel MR spectroscopy (intermediate TE) shows moderate elevation of the Choline (Cho) with mild to moderate depression of the N-acetyl aspartate (N-AA) and creatine (Cr) with increased Cho / Cr and Cho/NAA ratios. Single voxel MR spectroscopy (short TE) of the enhancing component of the lesion at the left high posterior frontal para-sagittal region shows elevation of the lipid / lactate.The spectroscopic findings are indicative of a malignant lesion.
- no hydrocephalic changes.
- normal cortical sulci.
- normal sellar region and posterior foss as well as the petromastoid system.
Bilateral fronto-parietal peri-ventricular and subependymeal mass lesion with infiltration of the forceps major and corpus callosum as described; the conventional and MR spectroscopic criteria is in favour of primary CNS lymphoma. The differential is high grade glioma (GBM), however the lack of significant perifocal oedema, mass effect and lack of typical pattern of thick irregular rind of enhancement as well as the multifocal subependymeal and periventricular nature of the lesion strongly suggests primary CNS lymphoma, rather than high grade glioma.