Limbic Encephalitis

36-year-old female who presented for new onset psychosis and hypersexuality of approximately 2 weeks duration. There is abnormal T2/FLAIR hyperintense signal involving the right frontal corona radiata, anterior striatocapsular regions, with prominent involvement of the caudate heads, anterior limbs of the internal capsules, anteromedial lentiform nuclei and bilateral hypothalami. There is mild diffusion restriction in the caudate heads and left putamen. The tissue edema and swelling results in partial effacement of the frontal horns and bodies of the lateral ventricles. There is no suspicious postcontrast enhancement. This is a case of limbic encephalitis of unknown etiology. The differential includes herpes encephalitis and diffuse astrocytoma. The patient was empirically treated with IV steroids and improved. Limbic encephalitis is the most common clinical paraneoplastic syndrome. It is thought to be immune-mediated by autoantibodies or cytotoxic T-cell mechanisms. Common clinical symptoms include memory loss, cognitive dysfunction, dementia, psychological features and seizures.