A Case of Anti-Leucine-Rich Glioma-Inactivated Protein 1 (Anti-LGI1) Encephalitis With an Unusual Frontomesial Motor Cortex T2 MRI Hyperintensity.

Anti-leucine-rich glioma-inactivated protein 1 (anti-LGI1) encephalitis is a rare autoimmune disorder, classified within limbic encephalitides, and characterized by seizures and subacute cognitive-behavioral impairment, mainly affecting short-term memory and usually involving temporo-mesial lobe structures. We present a case of anti-LGI1 encephalitis characterized by focal right lower limb motor seizures and pyramidal signs and responsive to high-dose methylprednisolone. The patient developed an atypical left frontal lobe parasagittal T2 hyperintense lesion on MRI within one month of hospital admission, which has not been described previously in this disease to the best of our knowledge.