paraneoplastic encephalitis with affinity for the limbic system. The limbic system is also involved in the much more common herpes virus (HV) encephalitis which is the major differential diagnosis. Clinical hallmarks of paraneoplastic limbic encephalitis are changing mental status with affective symptoms and memory impairment with subacute
onset. Men are more often affected than women. Small cell lung cancer is the extracranial malignancy most commonly associated with limbic encephalitis and has been identified in 2 - 3% of cases. An immunological or viral role in the aetiopathogenesis has been suggested. Pathological
and imaging findings are nonspecific and indistinguishable from those of HV encephalitis, consisting of bilateral T2
hyperintensities associated with variable postcontrast enhancement in the medial temporal
regions, insula and cingulate gyrus. Treatment of the primary malignancy may reverse the course of the disease in some cases.