Tumor mimicking demyelination

Multiple bilateral ovoid, periventricular and callososeptal T2 hyperintense, T1 hypointense lesions are demonstrated. The lesions are perpendicularly oriented to the ventricles. A right frontal juxtacortical lesion is also seen. There is moderate surrounding adjacent FLAIR / T2 high signal. Some of these are T1 hypointense. Several, however not all of these lesions demonstrate contrast enhancement.

A moderate to large area of right parietal cortical abnormality is seen, with edema / T2 high signal and associated vasogenic edema involving cortex and underlying white matter. There is vivid contrast enhancement within this region along with diffusion restriction (correspondingly low on ADC map) that mainly involves cortex. There is minimal mass effect for the degree of signal abnormality. No hemorrhage on EPI. No venous sinus thrombosis seen in non dedicated imaging.  No increase in cerebral blood volume.

Conclusion: Overall MRI finding favor demyelination with a tumefactive plaque in the right parietal region and multiple smaller active plaques elsewhere-- particularly consider ADEM or MS variants (such as Marburg's). (Angiocentric) malignancy or cerebral vasculitis are differentials.

The periventricular burden of FLAIR signal abnormality has progressed. The left frontal biopsy tract is noted with residual hemosiderin staining evident. The periventricular enhancement is again demonstrated and largely stable. The right occipital lesion has shown a discrete change in morphological appearance with increasing mass effect and prominent thickening of the occipital cortex. The surrounding FLAIR signal abnormality remains largely unchanged, however the gyriform pattern of enhancement is far more intense. Extensive restricted diffusion.

Conclusion: The evolution of the right occipital lesion is difficult to reconcile with demyelination, or evolving infarction and an alternative diagnosis should be sought. The possibility of all these changes representing CNS lymphoma should be entertained.