Dubey D, et al. - Researchers carried out this population-based comparative study to assess incidence and prevalence of autoimmune encephalitis and to compare the epidemiology of autoimmune and infectious encephalitis. They found similar prevalence and incidence of autoimmune encephalitis and infectious encephalitis. The detection of autoimmune encephalitis appeared to be increasing over time.

Methods

• The researchers conducted this study of the incidence and prevalence of autoimmune and infectious encephalitis in Olmsted County, USA.
• They defined autoimmune encephalitis diagnosis and subgroups by 2016 diagnostic criteria and infectious encephalitis diagnosis required a confirmed infectious pathogen.
• They calculated age- and sex-adjusted prevalence and incidence rates.
• They excluded patients with encephalitis of uncertain etiology.

Results

• The researchers found no significant difference between prevalence of autoimmune encephalitis on January 1, 2014, of 13.7/100,000 from that of all infectious encephalitides (11.6/100,000; p=0.63) or the viral subcategory (8.3/100,000; p=0.17).
• Between 1995-2015 the incidence rates of autoimmune and infectious encephalitis were 0.8/100,000 and 1.0/100,000 person-years respectively (p=0.58).
• For autoimmune, the number of relapses or recurrent hospitalizations was higher than infectious encephalitis (p=0.03).
• Increased incidence of autoimmune encephalitis was observed over time from 0.4/100,000 person-years (1995-2005) to 1.2/100,000 person-years (2006-2015) (p=0.02), attributable to the increased recognition of autoantibody-positive cases.
• Among African-Americans, the incidence (2.8 vs 0.7/100,000 person-years; p=0.01) and prevalence (38.3 vs 13.7/100,000; p=0.04) of autoimmune encephalitis was higher than Caucasians.
• As per the findings, the prevalence of specific neural autoantibodies was: myelin-oligodendrocyte-glycoprotein (MOG) (1.9/100,000); glutamic acid decarboxylase-65 (GAD65) (1.9/100,000); unclassified neural autoantibody (1.4/100,000); leucine-rich glioma-inactivated-protein-1 (LGI1) (0.7/100,000); collapsin response-mediator protein-5 (CRMP5) (0.7/100,000); N-methyl-D-aspartate-receptor (NMDAR) (0.6/100,000); anti-neuronal nuclear antibody-2 (ANNA-2/anti-Ri) (0.6/100,000) and glial fibrillary acidic protein-α (GFAPα) (0.6/100,000).