Objective: Evaluate the psychiatric presentation of anti-NMDAR encephalitis to identify features that help differentiate from a primary psychiatric disorder.

Background: Anti-NMDAR encephalitis results from antibodies binding the glycine subunit of the NMDA receptor, with consequent capping and internalisation of the receptor causing neuronal dysfunction. Presentation with psychiatric disturbance is common but identification of cases prior to neurological deterioration is difficult. Early treatment is associated with better outcomes, however, diagnosis requires CSF analysis which is not routinely performed.

Design/Methods: Retrospective review of all positive serum and CSF anti-NMDAR encephalitis cases in QLD, Australia between 2010 – 2018 and all published cases from inception of PubMed and Embase until Jan 2018. Comparison analysis with control cases of first episode psychosis with an anti-NMDAR antibody negative result.

Results: There were 706 cases identified in literature and 24 cases locally. These were typically young (mean 22.6 years), female (F:M ratio 3.5:1) and presented with significant behavioural disturbance. Psychosis was present in 45.8%. The most common psychiatric symptoms were severe agitation and aggression, abnormal speech and catatonia. In addition, prodromal cognitive deficits and antipsychotic sensitivity were seen before neurological deterioration in cases but not in the 103 control cases.

Conclusions: Several features including prodromal cognitive deficits, speech disturbance, antipsychotic sensitivity and catatonia are seen early in the course of anti-NMDAR encephalitis. These key features would not be typical of primary psychiatric disease and clinicians should have a low index of suspicion to proceed to lumbar puncture.

Disclosure: Dr. Warren has nothing to disclose. Dr. O’Gorman has nothing to disclose. Dr. Swayne has nothing to disclose. Dr. Siskind has nothing to disclose. Dr. Blum has nothing to disclose.