Figure 1. Antibody studies in a patient without tumour and extended clinical course.

An 18-year-old man was transferred from another hospital after 4 weeks’ of being in coma. At admission, his CSF and serum were assessed at dilution 1 in 40 for reactivity with HEK293 cells that recombinantly expressed NR1/NR2 heteromers of the NMDAR. Only the patient’s CSF was positive (A). B shows the reactivity of a monoclonal antibody against NR1, and co-localises with patient’s CSF reactivity (merged immunolabelling in C). D shows that the patient’s serum did not react with cells expressing NR1/NR2; in E these cells are immunolabelled by use of a monoclonal antibody against NR1. F shows the merged reactivities. In C and F the nuclei of the cells are stained with DAPI. The graph shows NMDAR antibody titres in CSF over time. Titres were measured by ELISA for 13 months. CSF from control individuals with disorders other than anti-NMDAR encephalitis (eg, stroke, encephalitis suspected to be autoimmune, cerebellar degeneration, and viral encephalitis) were less than 500 relative fluorescence units (RFU; data not shown). The patient was treated initially with corticosteroids and intravenous immunoglobulin (IVIg) without improvement, and subsequently with rituximab and monthly cyclophosphamide. During the clinical course the brain MRI showed mild generalised atrophy. He is currently at home and able to take care of himself, have normal conversations, and play computer games, but is still recovering from symptoms of frontotemporal dysfunction. All techniques have been described elsewhere.⁸ CSF=cerebrospinal fluid. NMDAR=N-methyl-D-aspartate receptor.