This case demonstrates tumefactive demyelination as a paraneoplastic disorder. It is a rare, locally aggressive form of demyelination ¹. In patients without a diagnosis of multiple sclerosis it can pose a diagnostic quandary and can often mimic a neoplasm. Peripheral diffusion restriction, a predilection for the periventricular and deep white matter, minimal mass effect and decreased perfusion leans the diagnosis towards tumefactive demyelination rather than malignancy ².

Paraneoplastic neurological disorders are remote manifestations of malignancy unrelated to metastases or the tumor itself. The greatest chance of neurological recovery comes from treating the associated malignancy and hence early diagnosis plays a vital role ³. 

Case contributed by Dr David Swienton and Dr Aanand Vibhakar