Quantitative brain ¹⁸F-FDG PET/CT analysis in seronegative autoimmune encephalitis

Area of Science:

• Neurology
• Nuclear Medicine
• Immunology

Background:

• Autoimmune encephalitis (AE) diagnosis can be challenging, especially in seronegative cases.
• Previous studies identified specific brain 18F-FDG PET/CT dysmetabolism patterns in anti-NMDAR and anti-LGI1 AE.
• Brain 18F-FDG PET/CT abnormalities in seronegative AE remain undescribed.

Purpose of the Study:

• To investigate brain 18F-FDG PET/CT findings in patients with seronegative autoimmune encephalitis.
• To identify common patterns of brain dysmetabolism in seronegative AE.
• To compare these patterns with those observed in anti-NMDAR and anti-LGI1 AE.

Main Methods:

• Cross-sectional analysis of brain 18F-FDG PET/CT data from patients with seronegative AE.
• Utilized NeuroQ™ software to calculate Z-scores for 47 brain regions.
• Compared findings with healthy controls and previously reported anti-NMDAR and anti-LGI1 AE cohorts.

Main Results:

• Eight probable and nine possible seronegative AE cases were analyzed.
• Both seronegative groups exhibited similar patterns of brain dysmetabolism.
• A consistent pattern of frontal lobe hypometabolism and medial temporal lobe hypermetabolism was observed, mirroring patterns in other AE types.
• Changes in PET/CT findings correlated with clinical status in four patients with serial scans.

Conclusions:

• A distinct 18F-FDG PET/CT pattern of frontal hypometabolism and medial temporal hypermetabolism may serve as a common biomarker for autoimmune encephalitis.
• This imaging pattern, combined with clinical data, could aid in earlier AE diagnosis and treatment initiation.
• Further research is warranted to validate this potential biomarker across diverse AE populations.