Positron emission tomography in autoimmune encephalitis: Clinical implications and future directions

Area of Science:

• Neuroimaging
• Nuclear Medicine
• Immunology

Background:

• Autoimmune encephalitis (AE) diagnosis can be challenging due to limitations in conventional methods like MRI, EEG, and CSF analysis.
• 18F-fluoro-deoxyglucose positron emission tomography (FDG-PET) offers a sensitive and reliable diagnostic tool for AE, particularly when other findings are scarce.
• FDG-PET has demonstrated abnormalities in AE cases where MRI results were normal.

Purpose of the Study:

• To summarize FDG-PET patterns in AE based on antibody subtypes.
• To evaluate the clinical outlook for FDG-PET in AE diagnosis and management.
• To explore the potential of FDG-PET in monitoring AE evolution and predicting functional outcomes.

Main Methods:

• Review and summarization of existing studies and case reports on FDG-PET in AE.
• Analysis of specific FDG-PET patterns associated with different AE antibody subtypes.
• Exploration of visual and quantitative FDG-PET assessment methods.

Main Results:

• Specific FDG-PET patterns were identified for different AE antibody subtypes, aiding in diagnosis.
• The anteroposterior gradient was common in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis.
• Medial temporal lobe hypermetabolism was observed in limbic encephalitis.

Conclusions:

• FDG-PET patterns are critical for identifying suspicious AE and correlate with antibody subtypes.
• Dynamic changes in FDG-PET metabolic presentation may help monitor AE evolution and predict outcomes.
• Further large, prospective studies are needed to standardize FDG-PET scanning protocols and validate quantitative analysis for AE evaluation.