Commenced him on treatment for myeloma- cyclopshophamide and dexamethsone as his serum paraprotein has risen to 10g/L over the last few weeks.

Syphilis serology was found to be positive and he was treated with benzylpenicillin, CSF syphilis was negative.

Histology suggested ADEM. 

Acute disseminated encephalomyelitis (ADEM) as the name would suggest, is featured by a monophasic acute inflammation and demyelination of white matter typically following a recent (1-2 weeks prior) viral infection or vaccination.

Imaging appearances vary from small punctate lesions to tumefactive regions, which have less mass effect than one would expect for their size, distributed in the supratentorial or infratentorial white matter. Compared to multiple sclerosis, involvement of the callososeptal interface is unusual. Lesions are usually bilateral but asymmetrical. Involvement of cerebral cortex, subcortical grey matter, especially the thalami, and the brainstem is not very common, but if present are helpful in distinguishing from multiple sclerosis.