PET/CT in the evaluation of anti-NMDA-receptor encephalitis: what we need to know as a NM physician

Anti N-methyl-D-aspartate receptor encephalitis (ANMDARE), also known as limbic encephalitis (LE), is a treatable rare disorder characterized by personality changes, irritability, depression, seizures, memory loss and sometimes dementia. It is classified under paraneoplastic syndrome (PNS) and produces antibodies against NR1 and NR2 subunits of glutamate aspartate receptor. It is thought to be closely related with malignancies like small cell lung cancer, ovarian teratoma and Hodgkin's lymphoma, apart from testis, breast and rarely gastric malignancies. Non-paraneoplastic encephalitis cases are the ones with no detectable malignancy and may be triggered by severe infection. As nuclear medicine physicians, we must be aware of the diverse presentation of ANMDARE or LE and should include a whole body positron emission tomography/computed tomography (PET/CT) and not just brain PET/CT during imaging. We describe the first case of PET/CT in an idiopathic ANMDARE Indian adolescent girl. (author)