Analysing triggers for anti-NMDA-receptor encephalitis including herpes simplex virus encephalitis and ovarian teratoma: results from the Queensland Autoimmune Encephalitis cohort

Abstract

Background: Anti-N-methyl-D-aspartate-receptor (anti-NMDA-R) encephalitis is a complex autoimmune neuropsychiatric syndrome. Although initially associated with ovarian teratoma, subsequent studies have demonstrated that anti-NMDA-R encephalitis may occur without an identifiable cause or be triggered by viral infection of the central nervous system such as herpes simplex virus encephalitis (HSVE).

Aim: To present details from a Queensland cohort analysing triggering events in patients with anti-NMDA-R encephalitis in an Australian context.

Methodology: The authors identified patients with anti-NMDA-R encephalitis diagnosed and managed through public hospitals in Queensland, Australia, between 2010 and the end of 2019. Data collected included demographics, clinical presentation, investigation results, management and outcome measurements.

Results: Thirty-one cases of anti-NMDA-R encephalitis were included in the study. Three cases of anti-NMDA-R encephalitis were triggered by prior HSVE, five cases were associated with ovarian teratoma and 23 cases had no identifiable trigger. There were an additional three cases in which anti-NMDA receptor antibodies were present in the context of other disease states but where the patient did not develop anti-NMDA-R encephalitis. Cases triggered by HSVE or associated with ovarian teratoma experienced a more severe disease course compared to cases with no identifiable trigger. All groups responded to immunosuppressive or immunomodulatory therapy. Analysis of clinical characteristics revealed a complex heterogeneous syndrome with some variability between groups.

Conclusion: In this cohort, the number of cases of anti-NMDA-R encephalitis triggered by HSVE is comparable to those triggered by ovarian teratoma. However, the majority of cases of anti-NMDA-R encephalitis had no identifiable trigger or associated disease process.

Keywords: CNS infection; anti-NMDA-R encephalitis; autoimmune encephalitis; herpes simplex virus encephalitis; ovarian teratoma.