Psychiatric phenomena as initial manifestation of encephalitis by anti-NMDAR antibodies

Objective Autoimmune encephalitis associated with autoantibodies against the N-methyl-d-aspartate receptor (NMDAR) often presents with behavioural change. Our objective was to describe in detail the psychiatric presentation and pathways to care in order to aid the early diagnosis of NMDAR encephalitis. Methods Sera and cerebrospinal fluid (CSF) from patients with suspected NMDAR encephalitis were tested on HEK 293 cells transfected with the NR1 subunit of the NMDAR. Clinical information was obtained from the referring psychiatrists and neurologists and by review of the clinical records. Results Samples from 15 patients (13 female, 2 male, mean age 24 years, range 5-56 years) tested anti-NMDAR positive. Twelve of the 15 patients (80%) presented with prominent psychiatric symptoms and 8 were initially referred to a psychiatric service. The most prominent initial psychiatric symptoms were anxiety in seven (47%), behavioural change (often bizarre) in six (40%) and agitation in five (33%). All patients developed psychiatric symptoms in the first 6 weeks of illness. Thirteen patients received psychotropic medications: antipsychotics in 12 and benzodiazepines in 11. Treating physicians considered the psychotropic medication not effective in 11 patients resul