Brain MRI showing progression of PML over four months

Progression of PML over four months in 47-year-old patient.
(A) At presentation, FLAIR MRI shows a small focus of hyperintensity signal in the left superior frontal gyrus.
(B) Two months later, the lesion has increased in volume and has developed a central focus of relatively decreased signal intensity (asterisk).
(C) Four months after initial presentation, the lesion is not only more extensive in the left frontal lobe, but there is also involvement of subcortical white matter in the right frontal subcortical white matter (arrow).