Paraneoplastic cerebellar degeneration (PCD) is still one of the most enigmatic of the autoimmune CNS disorders. It is relatively uncommon and is usually characterised by a rapid and severe cerebellar syndrome, leaving the patient dependent within a few weeks to months of onset. Brain imaging is usually remarkably unremarkable in PCD. Despite the presence of a very severe clinical deficit, the cerebellum is rarely affected radiologically at an early stage of the disease, although atrophy is usually seen some months after onset.

Three papers present unusual imaging features in PCD and provide some potential new insights into the pathogenesis of this disease (see pages 525, 529, 562 of this issue). The paper by Scheid et al reports cerebellar atrophy occurring within …