Abstract
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. 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: ((PET) OR (positron emission tomography)) AND ((FDG) OR (fluorodeoxyglucose)) AND ((encephalitis) OR (brain inflammation)). Studies had to satisfy the following criteria: (i) include at least ten pediatric or adult patients suspected or diagnosed with autoimmune encephalitis according to the current recommendations, (ii) 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 this systematic review, according to a meta-analysis following the PRISMA method, and selected publication quality was assessed with the QUADAS-2 tool. The search strategy identified 626 articles including references from publications. The detection sensitivity of 18F-FDG PET was 87% (80-92%) based on 21 publications and 444 patients included in the meta-analysis. We also report specific brain 18F-FDG PET imaging patterns for the main encephalitis autoantibody subtypes. 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.
Highlights
Encephalitis is defined as a debilitating neurological disorder that develops as a rapidly progressive encephalopathy caused by brain inflammation 1
Specific metabolic 18F-FDG Position Emission Tomography (PET) patterns corresponding to the main autoimmune encephalitis autoantibody subtypes further enhance the value of this diagnostic
A further 256 publications reporting on non-original cases were excluded. 329 full-text publications were reviewed and considered for autoimmune encephalitis 18F-FDG PET and MRI detection sensitivity
Summary
Encephalitis is defined as a debilitating neurological disorder that develops as a rapidly progressive encephalopathy caused by brain inflammation 1. Even though this pathology is relatively rare 2, its prognosis is poor, entailing serious irreversible sequelae and death in up to 7–12% of cases [3,4]. Encephalitis can be subdivided into two main etiologies: infectious (40–52% of cases5) and immune mediated (about 21%4), which include the paraneoplastic syndromes, with the remaining cases of unknown origin(s) 6,7,8,9. Our current study focuses on autoimmune encephalitis, including paraneoplastic encephalitis, associated with onconeuronal antibodies. Autoimmune encephalitis is characterized by the presence of autoantibodies (aAbs) against neuronal targets 10. We reviewed encephalitis by aAb subtype, in terms of onconeuronal and non-onconeuronal Abs, since this classification appears to more closely reflect the clinical presentation 11
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