Clinical characteristics and short-term outcomes of autoimmune encephalitis in adults

Abstract

To characterize clinical, paraclinical features and short-term outcomes in different types of autoimmune encephalitis (AE) in a one-center cohort of Russian patients, as well as to evaluate the frequency and significance of the joint expression of antineuronal and anti-glial antibodies (Abs) in AE. Forty-one patients were diagnosed with AE at the Research Center of Neurology from November 2020 to December 2022. Demographic, clinical characteristics, results of laboratory tests, MRI of brain, treatment and outcomes of disease were analyzed. The analysis of Abs to glial antigens (myelin-oligodendrocyte glycoprotein - MOG, glial fibrillar acidic protein - GFAP, aquaporin 4 - AQP-4) was performed by indirect immunofluorescence assay (Euroimmun, Germany). In 24 (58.5%) patients was established definite AE, confirmed by specific Abs detection; in 2 (4.9%) - definite limbic encephalitis, in 15 (36.6%) - seronegative probable AE (including 3 cases of Hashimoto's encephalitis). GFAP-Abs in cerebrospinal fluid (CSF) were detected only in two patients - with clinical and MRI-picture of autoimmune GFAP-astrocytopathy (A-GFAP-A). GFAP- and MOG-Abs in the blood were detected in 25.7% and 6%, respectively, AQP-4-Abs were not detected. There were no correlations between co-expression with glial Abs and clinical characteristics. Systemic and antithyroid Abs were present in 15% and 31%, respectively. Paraneoplastic AE accounted for 22%. For the first time in the Russian population, 2 cases of A-GFAP-A, 6 cases of AE associated with COVID-19 were described. The most common first syndrome were epileptic seizure (34%), psychiatric (29%) and cognitive (14%) disorders. Relapses of AE was observed in 22%. Inflammatory changes in CSF were detected in 41%, focal changes on MRI in 68%. First-line immune therapy was performed in all patients, 85% of cases received pulse therapy with methylprednisolone. Second-line immune therapy (rituximab or cyclophosphamide intravenously) was performed in 19.5%, 78% of patients achieved significant improvement during treatment (scores ≤2 on the modified Rankin scale). The results allow us to consider COVID-19 as a trigger of AE. The absence of detection of GFAP-Abs in CSF in patients with other types of AE contributes to the confirmation of the specificity of GFAP-seropositivity of CSF for the diagnosis of A-GFAP-A. The expression of GFAP- and MOG-Abs in AE can serve as confirmation of the immuno-mediated etiology of the disease, which is especially important for the AE diagnosis in the absence of antineuronal Abs.