Extensive deep white matter signal change demonstrated on both FLAIR and T2. The signal change extends to the subcortical region and also involves the splenium of the corpus callosum. The signal change appears more extensive posteriorly. No contrast enhancement of these areas or abnormal enhancement elsewhere. The posterior fossa appears uninvolved.
The time of flight and post contrast MRA (not shown) demonstrate normal anatomical variance with a foetal origin of the right PCA. There is no evidence of stenosis, or mural enhancement of the circle of Willis vasculature to suggest vasculitis.
CONCLUSION:
There is extensive bilateral white matter FLAIR signal change which is increased since the previous examination. The differential diagnosis includes demyelination (including ADEM) despite the patient's age. Other possibilities include vasculitis or intravascular lymphoma.