107 A tail of two NMDA receptor antibody encephalitidies: aggressive treatment, divergent outcomes

Background Autoimmune encephalitis is an increasingly recognised disease that presents with seizures, neuropsychiatric symptoms, dystonic movements, and autonomic dysfunction1. As the mainstay of treatment immunosuppressive therapies are most effective when subject to early initiation and timely escalation, both of which are recognised to affect outcomes2. Nevertheless approximately half of patients with NMDA-R antibody encephalitis do not respond adequately to first-line therapy, and a significant proportion (12-30%) relapse2. Cases A 19 year old lady presented with new-onset seizures and psychosis. EEG showed focal spike-and-wave discharges and MRI brain a focal area of restricted diffusion consistent with recent seizure activity. NMDA-R antibodies were present in both CSF and serum. Following early treatment with corticosteroid, plasma exchange, IVIG and rituximab the patient recovered, returning to college after 6 months. A 50 year old gentleman presented with a two day history of myalgias and confusion. EEG showed spike-and-wave discharges and MRI brain increased T2 signal in the mesial temporal lobes. NMDA-R antibodies were present in both CSF and serum. He was treated with corticosteroid, plasma exchange, IVIG and rituximab, and continued on oral prednisone and mycophenolate. Response to treatment was poor with persistent ongoing physical and cognitive impairment at 6 months. Serial MRI showed substantial (~30%) loss of parenchymal brain volume. Discussion These cases illustrate that timely and aggressive management of NMDA-R antibody encephalitis with favourable prognostic markers is no guarantee of recovery. Several novel clinical and immunological predictors of response to therapy have been postulated, and currently await broader validation.3 References Dalmau J, Graus F. Antibody-mediated encephalitis. N Engl J Med 2018 Mar 1;378(9):840–851. Titulaer MJ, McCracken L, Gabilondo I, Armangue T, Glaser C, Iizuka T, et al. Treatment and prognostic factors for long-term outcome in patients with anti-NMDA receptor encephalitis: an observational cohort study. Lancet Neurol 2013;12(2):157–65. Ruegg S, Yeh EA, Honnorat J. Forecasting outcomes in anti-NMDAR encephalitis: clearer prognostic markers needed. Neurology 2019 Jan 15;92(3):119–120.