How would you modify your differential diagnosis on the basis of this scan?
Scattered areas of leptomeningeal, gyral and tentorial dural enhancement with associated bright FLAIR signal, along with more nodular enhancement in deep right cerebrum suggests the following entities: intravascular lymphoma; primary cerebral angiitis; neurosarcoid or granulomatous vasculitis.
What imaging is most sensitive to the changes of vasculitis?
Catheter digital subtraction angiography (DSA), although even in many histology proven cases, angiography is negative.
There is bright FLAIR/T2 signal involving the left mesial temporal lobe extending posteriorly to involve the left occipital lobe and splenium of the corpus callosum. Small areas of liquefaction are seen within the left splenium and hippocampal body. 2.0 cm area of bright T2/FLAIR signal is also seen adjacent to the anterior body of the right lateral ventricle.
There are patchy leptomeningeal- and gyral-pattern of enhancement seen involving the left parahippocampal gyrus extending into the occipital lobe. Perivenular leptomeningeal enhancement and bright FLAIR/T2 signal are seen in periventricular deep white matter bilaterally. Scattered nodular enhancement are also seen along the right lateral ventricle, centrum semiovale, caudate head and thalamus. There is also tentorial dural thickening and enhancement.
No definite area of diffusion restriction seen, with bright DWI signal due to T2* shine through.
MRS over the right periventricular bright signal demonstrate increased Cho and reduced NAA even after allowing for baseline shift. This however is nonspecific. MRA is unremarkable (not shown).