Objective: To consolidate current understanding of detection sensitivity of brain 18F-FDG PET scans in the diagnosis of autoimmune encephalitis and to define specific metabolic imaging patterns for the most frequently occurring autoantibodies. Methods: A systematic and exhaustive search of data available in the literature was performed by querying the PubMed/MEDLINE and Cochrane databases for the search terms: "FDG PET" and “"encephalitis" or "brain inflammation"”. Studies had to satisfy the following criteria: i. include at least one patient suspected or diagnosed with autoimmune encephalitis according to the current recommendations, ii. be an original case-report iii. specifically present 18F-FDG PET and/or morphologic imaging findings. The diagnostic 18F-FDG PET detection sensitivity in autoimmune encephalitis was determined for all cases reported in the literature and a meta-analysis, according to the PRISMA method, was performed on a subset of these, which included PET scans for at least 10 patients, and whose quality was assessed with the QUADAS-2 tool.Results: The search strategy identified 1113 articles. The detection sensitivity of 18F-FDG PET was 90%, based on 176 publications and 720 patients and 80% [75%-84%] by meta-analysis based on 21 publications and 444 patients. We also report specific brain 18F-FDG PET imaging patterns for the main encephalitis autoantibody subtypes.Conclusion and Relevance: Brain 18F-FDG PET has a high detection sensitivity and should be included in future diagnostic autoimmune encephalitis recommendations. Specific metabolic 18F-FDG PET patterns corresponding to the main autoimmune encephalitis autoantibody subtypes further enhance the value of this diagnostic.