Extensive deep white matter signal change is 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, and there is corresponding high DWI signal, some of which has low ADC values (not shown). Possible punctate regions of contrast enhancement within these areas, some of which may be artifactual, are present. The posterior fossa appears uninvolved.
The time of flight and post-contrast MRA (not shown) demonstrate no evidence of stenosis or mural enhancement of the circle of Willis vasculature to suggest vasculitis.
Conclusion:
The differential diagnosis includes demyelination (including ADEM) despite the patient's age. Other possibilities include vasculitis or intravascular lymphoma.