RT Journal Article SR Electronic T1 Paraneoplastic tumefactive demyelination with underlying combined germ cell cancer JF Practical Neurology JO Pract Neurol FD BMJ Publishing Group Ltd SP 451 OP 455 DO 10.1136/practneurol-2015-001146 VO 15 IS 6 A1 Jack R Broadfoot A1 Hilary A Archer A1 Elizabeth Coulthard A1 Auke P A Appelman A1 Judit Sutak A1 Jeremy P Braybrooke A1 Seth Love YR 2015 UL http://pn.bmj.com/content/15/6/451.abstract AB Paraneoplastic demyelination is a rare disorder of the central nervous system. We describe a 60-year-old man with tumefactive demyelination who had an underlying retroperitoneal germ cell cancer. He presented with visuospatial problems and memory loss and had a visual field defect. His MRI was interpreted as a glioma but stereotactic biopsy showed active demyelination. Investigation for multiple sclerosis was negative but CT imaging showed retroperitoneal lymphadenopathy, and nodal biopsy confirmed a combined germ cell cancer. He responded poorly to corticosteroid treatment, and his visual field defect progressed. However, 6 months after plasma exchange and successful chemotherapy, he has partially improved clinically and radiographically. Tumefactive demyelination is typically associated with multiple sclerosis but may be paraneoplastic. It is important to recognise paraneoplastic tumefactive demyelination early, as the neurological outcome relies on treating the associated malignancy.