121. Differences Between Auto-Antibody Titres in Cerebrospinal Fluids and Sera of Patients With Anti-N-methyl-D Receptor Encephalitis

Abstract

Abstract Anti--methyl-D-aspartate receptor (NMDAR) encephalitis is one of autoimmune limbic encephalitis which receives the most attention in the psychiatric field. Patients with anti-NMDAR encephalitis typically exhibit psychiatric symptoms such as hallucination, delusion, aggression, manic episodes, and abnormal behaviors. With the given psychiatric symptoms, those patients are often diagnosed as atypical psychosis or schizophrenia and medicated with antipsychotic drugs. The definite diagnosis of anti-NMDAR encephalitis still remains to be established, however. The subjects were the patients whose cerebrospinal fluids (CSF) were verified to contain anti-NMDAR1 receptor (GRIN1) auto-antibodies and thus were diagnosed as anti-NMDAR encephalitis. These subjects exhibited chronic or subacute symptoms which were classified into typical psychosis (21 patients) and atypical psychosis (20 patients). We measured the immunoreactivity for NMDAR1 in the cell-based immunoassay in all CSF samples as well as in some of their serum samples (37 patients). This study was approved by the authorization of the Kanazawa Medical College Ethics Committee and Niigata University Medical Ethics Committee. All the patients provided written informed consent to allow the use of CSF and blood samples for this investigation. Although all the CSF samples were positive for the auto-antibodies, the positive frequency of their blood samples was lower in the subjects with atypical psychosis (23.5%; 4 patients) than in those with typical psychosis (65.0%; 13 patients) ( < .05). In addition, the auto-antibody titres were significantly lower in both CSF ( < .05) and serum ( < .01) of the subjects with atypical psychosis. These results suggest that the patients with anti-NMDAR encephalitis, but not with typical psychotic symptoms, often exhibit lower or undetectable blood concentrations of anti-NMDAR1 auto-antibodies. Thus, the definite diagnosis of anti-NMDAR encephalitis requires CSF examination.